Ion beam device

ABSTRACT

Provided is an ion beam device provided with a gas electric field ionization ion source which can prevent an emitter tip from vibrating in a non-contact manner. The gas electric field ionization ion source is comprised of an emitter tip ( 21 ) for generating ions; an emitter base mount ( 64 ) for supporting the emitter tip; an ionizing chamber which has an extraction electrode ( 24 ) opposed to the emitter tip and which is configured so as to surround the emitter tip ( 21 ); and a gas supply tube ( 25 ) for supplying gas to the vicinity of the emitter tip. The emitter base mount and a vacuum container magnetically interact with each other.

TECHNICAL FIELD

The present invention relates to an ion beam device such as an ionmicroscope or an ion beam machining device, a composite device of an ionbeam machining device and an ion microscope, and a composite device ofan ion microscope and an electron microscope. The invention also relatesto an analysis/inspection device to which an ion microscope and anelectron microscope are applied.

BACKGROUND ART

When a sample is irradiated while scanning with electrons and secondarycharged particles released from the sample are detected, the structureof the surface of the sample can be observed. This is called a scanningelectron microscope (hereinbelow, abbreviated as SEM). On the otherhand, also by irradiating a sample while scanning with an ion beam anddetecting secondary charged particles released from the sample, thestructure of the sample surface can be observed. This is called ascanning ion microscope (hereinbelow, abbreviated as SIM). Particularly,when a sample is irradiated with an ion species which is light in masssuch as hydrogen or helium, sputtering action becomes relatively small,and it becomes suitable to observe a sample.

Further, the ion beam is more sensitive to information of a samplesurface as compared with an electron beam. The reason is that anexcitation region of secondary charged particles locally exists more inthe sample surface as compared with irradiation of the electron beam. Inthe electron beam, since the nature as waves of electrons cannot beignored, an aberration is caused by the diffractive effect. On the otherhand, since the ion beam is heavier than electrons, the diffractiveeffect can be ignored.

By irradiating a sample with an ion beam and detecting ions passedthrough the sample, information in which the structure of the inside ofthe sample can also be obtained. This is called a transmission ionmicroscope. In particular, by irradiating a sample with an ion specieswhich is light in mass such as hydrogen or helium, the ratio of passingthrough the sample increases, and it is preferable for observation.

On the other hand, by irradiating a sample with an ion species which isheavy in mass such as argon, xenon, or gallium, it is preferable toprocess the sample by sputtering action. In particular, a focused ionbeam (hereinbelow, abbreviated as FIB) device using a liquid metal ionsource (hereinbelow, abbreviated as LMIS) is known as an ion beamprocessor. In recent years, a composite FIB-SEM device of a scanningelectron microscope (SEM) and a focused ion beam (FIB) is also used. Inthe FIB-SEM device, by forming a square hole in a desired place withirradiation of an FIB, a section can be SEM-observed. A sample can alsobe processed by generating a gas ion of argon, xenon, or the like by aplasma ion source or a gas field ion source and irradiating a samplewith the gas ion.

In the ion microscope, a gas field ion source is preferable as the ionsource. The gas field ion source supplies gas of hydrogen, helium, orthe like to a metal emitter tip having a tip curvature radius of about100 nm, applies a high voltage of a few kV or higher to the emitter tipto ionize gas molecules, and extracts the resultant as an ion beam. Ascharacteristics, the ion source can generate an ion beam having a narrowenergy width and, since the size of the ion generation source is small,generate a fine ion beam.

In the ion microscope, to observe a sample at a high signal-noise ratio,an ion beam of high current density has to be obtained on a sample. Forthis purpose, the ion radiation angle current density of the ionizationion source has to be made high. To make the ion radiation angle currentdensity high, it is sufficient to increase molecule density of ionmaterial gas (ionization gas) in vicinity of the emitter tip. The gasmolecular density per unit pressure is inversely proportional totemperature of gas. Consequently, it is sufficient to cool the emittertip to extremely low temperature and decrease the temperature of gasaround the emitter tip to low temperature. By the operation, themolecule density of the ionization gas in the vicinity of the emittertip can be made high. The pressure of the ionization gas around theemitter tip can be set to, for example, about 10⁻² to 10 Pa.

However, when the pressure of the ion material gas is set to 1 Pa orhigher, the ion beam collides with neutral gas, and the ion currentdecreases. When the number of gas molecules in the field ion sourcebecomes large, the frequency that gas molecules which collide with thewall of a high-temperature vacuum vessel and come to have hightemperature collide with the emitter tip increases. Due to this, thetemperature of the emitter tip rises, and the ion current decreases.Consequently, the field ion source is provided with an ionizationchamber mechanically surrounding the emitter tip. The ionization chamberis formed by using an ion extraction electrode provided so as to beopposed to the emitter tip.

Patent Reference 1 discloses a method of improving the ion sourcecharacteristic by forming a small projection at the end of the emittertip. Non-patent Reference 1 discloses a method of manufacturing thesmall projection at the end of the emitter tip by using a second metaldifferent from the material of the emitter tip. Non-patent Reference 2discloses a scanning ion microscope having a gas field ion source forion-emitting helium.

Patent Reference 2 discloses a method of providing, in positions apartfrom each other in the circumferential direction of a side wall of avacuum vessel of an ion source, a plurality of supporting pieces forvibration prevention extending from the inner face of the side walltoward the ion source and whose length can be adjusted from the outsideso as to penetrate, and sandwiching a heat insulating material betweenthe inner end of each of the supporting piece and the supporting face topress the ion source, thereby preventing vibration of the ion source.However, inflow of heat from the supporting pieces to the ion source isnot considered.

Patent Reference 3 discloses a method of making a spherical device floatin a predetermined position over a superconductor material at the timeof exposing the sphere device to light.

Patent Reference 4 discloses a liquid metal ion source having aneedle-shaped member as an ion emitter, an extraction electrode, and anacceleration electrode, wherein an opening through which an extractedion passes is provided on the side opposed to the needle-shaped memberof the acceleration electrode, and a shield member for preventingsputter particles generated by collision of the extracted ions with eachother or with the acceleration electrode from reaching the needle-shapedmember is provided.

Patent Reference 5 discloses an electron beam device having a movablediaphragm which can be inserted from a passage of an electron beam,wherein a spare chamber which is communicated with the electron beamdevice body in vacuum and can be shielded by air lock means, and meansfor evacuating the spare chamber are provided, and the movable diaphragmis moved to the spare chamber without exposing the electron beam devicebody to atmosphere, and can be replaced. In the device, without exposingthe electron beam device body to atmosphere, the movable diaphragm whichis contaminated can be easily replaced or cleaned.

Patent Reference 6 discloses a charged particle beam device which isdownsized by using a non-evaporable Getter pump, not an ion pump, asmain exhaust means of the electron source.

Patent Reference 7 discloses a gas field ion source provided with achange-over switch for connecting a high-voltage lead-in wire for theextraction electrode to a high-voltage lead-in wire for the emitter tip.In the gas field ion source, after forced discharge process between theion source outer wall and the emitter tip, that is, so-calledconditioning process, discharge between the emitter tip and theextraction electrode can be prevented.

Patent Reference 8 proposes an apparatus for observing and analyzing afailure, a foreign matter, or the like by forming a square hole near anabnormal place in a sample with an FIB and observing the section of thesquare hole by an SEM device.

Patent Reference 7 proposes a technique of extracting a small sample fortransmission electron microscope observation from a bulk sample by usingan FIB and a probe.

RELATED-ART DOCUMENTS

Patent Documents

-   Patent Reference 1: Japanese Unexamined Patent Application    Publication No. S58-85242-   Patent Reference 2: Japanese Unexamined Patent Application    Publication No. H07-282759-   Patent Reference 3: Japanese Unexamined Patent Application    Publication No. 2001-167999-   Patent Reference 4: Japanese Unexamined Patent Application    Publication No. 2003-123569-   Patent Reference 5: Japanese Unexamined Patent Application    Publication No. H04-286843-   Patent Reference 6: Japanese Unexamined Patent Application    Publication No. 2007-311117-   Patent Reference 7: Japanese Unexamined Patent Application    Publication No. 2002-150990-   Patent Reference 8: WO99/05506    Non-Patent References-   Non-patent Reference 1: H.-S. Kuo, I.-S. Hwang, T.-Y. Fu, J.-Y. Wu,    C.-C. Chang, and T. T. Tsong, Nano Letters 4 (2004), p. 2379-   Non-patent Reference 2: J. Morgan, J. Notte, R. Hill, and B. Ward,    Microscopy Today, July 14, (2006), p. 24

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

A gas field ion source having a nano-pyramid structure at the tip of aconventional metal emitter has the following challenges. Thecharacteristic of the ion source is use of an ion released from vicinityof one atom at the tip of the nano-pyramid. That is, the region fromwhich the ion is released is narrow, and the ion light source has asmall size of a nanometer or less. Consequently, by focusing the ionlight source onto a sample at the same magnification or increasing thereduction ratio to about 1/2, the characteristic of the ion source canbe maximally utilized. In a conventional gallium liquid metal ionsource, the dimension of the ion light source is estimated as about 50nm. Therefore, to realize a beam diameter of 5 nm on a sample, thereduction ratio has to be set to 1/10 or less. In this case, vibrationof the emitter tip of the ion source is reduced to 1/10 or less on asample. For example, even when the emitter tip vibrates by 10 nm, thevibration of a beam spot on a sample becomes 1 nm or less. Therefore,the influence of vibration of the emitter tip on the beam diameter of 5nm is small. However, in the example, the reduction ratio is relativelylarge and is about 1 to 1/2.

Therefore, in the case where the reduction ratio is 1/2, the vibrationof 10 nm at the emitter tip becomes vibration of 5 nm on a sample, thevibration of the sample for the beam diameter is large. That is, forexample, to realize resolution of 0.2 nm, the vibration of the emittertip has to be set to 0.1 nm or less at the maximum. The conventional ionsource is not always sufficient from the viewpoint of prevention ofvibration at the emitter tip.

The inventors of the present invention have paid attention to the facethat a slight vibration at the emitter tip deteriorates the resolutionof an observation image. From the viewpoint, there was an attempt toprevent vibration of the ion source by a supporting piece from the sidewall of a vacuum vessel of an ion source. However, inflow of heat to theion source via the supporting member is not considered. There is aproblem such that the ion source brightness deteriorates due to rise inthe temperature of the ion source. There is also a problem that thesupporting member is deformed by cooling of the ion source. Theinventors of the present invention found that by maintaining the lowtemperature of the ion light source and solving the problem ofdeformation in the supporting member by the cooling, the performance ofthe ion source can be maximally utilized.

As described above, the gas field ion source ionizes gas of helium orthe like by a sharp emitter tip and extracts the resultant as an ionbeam. When impurity is included in the gas molecules, there is a casesuch that the impurity is adhered to the vicinity of the emitter tip.When the helium which approaches the emitter tip is ionized, supply ofthe helium to the tip of the nano-pyramid decreases, and ion beamcurrent decreases. That is, the existence of impurity gas makes the ionbeam current unstable. The conventional ion source is not alwayssufficient from the viewpoint of reduction of impurity gas to theemitter tip. Particularly, consideration on gas generated when a beamlimiting aperture or the like is irradiated with an ion beam is notsufficient.

The inventors of the present invention found a problem such thatimpurity gas or the like contained in gas generated when a limitingaperture or the like is irradiated with an ion beam, gas flowing from asample chamber side to an ion source vacuum vessel, or an ion materialgas supplied to an ion source is adhered to the end of the emitter tipand makes the ion beam current unstable.

An object of the present invention is to provide an ion beam devicerealizing high-resolution sample observation by reducing vibration of anemitter tip for a gas field ion source and to provide an ion beam devicewith a stable ion beam and realizing sample observation withoutbrightness unevenness in an observation image.

Another object of the present invention is to provide a device ofobserving a section by an ion microscope and a section observing methodby processing a sample with an ion beam to form a section and, in placeof a device of observing a section by an electron microscope, forming asection by process with an ion beam and observing the section by an ionmicroscope.

Another object of the present invention is to provide a device capableof performing sample observation by an ion microscope, sampleobservation by an electron microscope, and an element analysis by asingle device, an analyzing device for observing and analyzing a defect,a foreign matter, or the like, and an inspection device.

Means for Solving the Problems

According to the present invention, an ion beam device includes: a gasfield ion source for generating an ion beam; an ion lens for focusing anion beam extracted from the gas field ion source on a sample; a movablebeam limiting aperture which limits an open angle of the ion beam to theion lens; a sample stage on which the sample is mounted; and a vacuumvessel which houses the gas field ion source, the ion lens, the beamlimiting aperture, the sample stage, and the like. The gas field ionsource includes an emitter tip for generating an ion, an emitter basemount which supports the emitter tip, an ionization chamber having anextraction electrode provided so as to be opposed to the emitter tip andconstructed so as to surround the emitter tip, and a gas supply pipe forsupplying gas to vicinity of the emitter tip, and a mechanism whichproduces a noncontact magnetic interaction between the emitter basemount and the vacuum vessel is provided.

According to the invention, in the ion beam device, a part of theemitter base mount is made of a superconducting material.

According to the invention, in the ion beam device, when the beamlimiting aperture is a hole opened in a plate, the irradiation directionof an ion beam and a normal to the plate have a tilt relation.

EFFECT OF THE INVENTION

The invention provides the ion beam device realizing high-resolutionsample observation by reducing vibration of an emitter tip for a gasfield ion source. An ion beam device realizing sample observationwithout brightness unevenness in an observation image using a stable ionbeam is provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of a first example of an ionmicroscope according to the present invention.

FIG. 2 is a schematic configuration diagram of a control system of thefirst example of the ion microscope according to the present invention.

FIG. 3 is a schematic structure diagram of a cooling mechanism of a gasfield ion source in the first example of the ion microscope according tothe invention.

FIG. 4 is a schematic structure diagram of the gas field ion source inthe first example of the ion microscope according to the invention.

FIG. 5 is a cross section of a vibration preventing mechanism of the gasfield ion source in the first example of the ion microscope according tothe invention.

FIG. 6 is a schematic structure diagram of the vibration preventingmechanism of the gas field ion source in the first example of the ionmicroscope according to the invention.

FIG. 7 is a schematic structure diagram of an ionization chamber in thegas field ion source in the first example of the ion microscopeaccording to the invention.

FIG. 8 is a schematic configuration diagram showing a beam limitingaperture tilt in the first example of the ion microscope according tothe invention.

FIG. 9 is a schematic configuration diagram of an ionization materialpurifying mechanism in the first example of the ion microscope accordingto the invention.

FIG. 10 is a schematic configuration diagram of a second example of anion microscope according to the invention.

FIG. 11 is a schematic structure diagram of a vibration preventingmechanism of the gas field ion source in the second example of the ionmicroscope according to the invention.

FIG. 12 is a schematic configuration diagram of a third example of theion microscope according to the invention.

FIG. 13A is a diagram for explaining operation of a mechanism of cuttinga wire (connected state) in the periphery of an ionization chamber of agas field ion source in a fourth example of the ion microscope accordingto the invention.

FIG. 13B is a diagram for explaining operation of a mechanism of cuttinga wire (cut state) in the periphery of the ionization chamber of the gasfield ion source in the fourth example of the ion microscope accordingto the invention.

MODES FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, an example of an ion beam device according to thepresent invention will be described. In the following, a first exampleof a scanning ion microscope device as an ion beam device will bedescribed. The scanning ion microscope of the example has a gas fieldion source 1, an ion beam irradiation system column 2, a sample chamber3, and a cooling mechanism 4. The ion beam irradiation system column 2and the sample chamber 3 are held in vacuum. The ion beam irradiationsystem has an electrostatic-type condenser lens 5, a beam limitingaperture 6, a beam scanning electrode 7, and an electrostatic-typeobjective lens 8. In the sample chamber 3, a sample stage 10 on which asample 9 is mounted, and a secondary particle detector 11 are provided.The sample 9 is irradiated with an ion beam 14 from the gas field ionsource 1 via the ion beam irradiation system. A secondary particle beamfrom the sample 9 is detected by the secondary particle detector 11.Although not shown, an electron gun for neutralizing charge-up of thesample irradiated with the ion beam and a gas gun for supplying etchingor deposition gas close to the sample are provided.

The cooling mechanism 4 has a refrigerator 40 for cooling the gas fieldion source 1. In the ion microscope of the example, a center axial line40A of the refrigerator 40 is disposed in parallel to an optical axis14A of the ion beam irradiation system.

The ion microscope of the example further includes an ion sourceevacuation pump 12 for evacuating the gas field ion source 1 and asample chamber evacuation pump 13 for evacuating the sample chamber 3.

On a device stand 17 disposed on a floor 20, a base plate 18 is disposedvia a vibration preventing mechanism 19. The gas field ion source 1, thecolumn 2, and the sample chamber 3 are supported by the base plate 18.

The device stand 17 is provided with a support pillar 103. Therefrigerator 40 is supported by the support pillar 103. Vibration of therefrigerator 40 is transmitted to the device stand 17 via the supportpillar 103. However, the vibration of the refrigerator 40 which isreduced by the vibration preventing mechanism 19 is transmitted to thebase plate 18.

On the floor 20, a compressor unit (compressor) 16 using, for example,helium gas as operation gas is installed. A helium gas of high pressureis supplied to the refrigerator 4 of, for example, a Gifford-McMahontype (GM type) via a pipe 111. When the helium gas of high pressureperiodically expands in the GM-type refrigerator, cold is generated. Thelow-pressure helium gas which is expanded and comes to have low pressureis collected by the compressor unit via a pipe 112.

The vibration of the compressor unit (compressor) 16 is transmitted tothe device stand 17 via the floor 20. The vibration preventing mechanism19 is disposed between the device stand 17 and the base plate 18, andthere is a characteristic such that the high-frequency vibration of thefloor is not easily transmitted to the gas field ion source 1, the ionbeam irradiation system column 2, the vacuum sample chamber 3, and thelike. Therefore, there is a characteristic such that the vibration ofthe compressor unit (compressor) 16 is not easily transmitted to the gasfield ion source 1, the ion beam irradiation system column 2, and thesample chamber 3 via the floor 20. In the above description, the causeof the vibration of the floor 20 is the refrigerator 40 and thecompressor 16. However, the cause of the vibration of the floor 20 isnot limited to the above.

The vibration preventing mechanism 19 may be a vibration-proof rubber, aspring, a damper, or a combination of them. The base plate 18 isprovided with a support pillar 104. The lower part of the coolingmechanism 4 is supported by the support pillar 104, which will bedescribed later with reference to FIG. 3.

Although the vibration preventing mechanism 19 is provided on the devicestand 17 in the example, the vibration preventing mechanism 19 may beprovided for the leg of the device stand 17. The vibration preventingmechanism 19 may be provided both on the stand 17 and for the leg of thedevice stand 17.

FIG. 2 illustrates an example of a control system of the ion microscopeaccording to the present invention shown in FIG. 1. The control systemof the example has a gas field ion source controller 91 for controllingthe gas field ion source 1, a refrigerator controller 92 for controllingthe refrigerator 40, a lens controller 93 for controlling the condenserlens 5, a beam limiting aperture controller 94 for controlling the beamlimiting aperture 6, an ion beam scanning controller 95 for controllingthe beam scanning electrode 7, a secondary particle detector controller96 for controlling the secondary particle detector 11, a sample stagecontroller 97 for controlling the sample stage 10, an evacuation pumpcontroller 98 for controlling the sample chamber evacuation pump 13, anda computer processor 99 for performing various arithmetic operations.The computer processor 99 has an image display unit. The image displayunit displays an image generated from a detection signal of thesecondary particle detector 11 and information which is input by inputmeans.

The sample stage 10 has a mechanism of linearly moving the sample 9 intwo orthogonal directions in the sample mount plane, a mechanism oflinearly moving the sample 9 in a direction perpendicular to the samplemount plane, and a mechanism of turning the sample 9 in the sample mountplane. The sample stage 10 further has a tilting function capable ofvarying the irradiation angle to the sample 9 of the ion beam 14 byturning the sample 9 about the tilt axis. The controls are executed bythe sample stage controller 97 in accordance with an instruction fromthe computer processor 99.

The operation of the ion beam irradiation system of the ion microscopeof the example will be described. The operation of the ion beamirradiation system is controlled by an instruction from the computerprocessor 99. The ion beam 14 generated by the gas field ion source 1 iscondensed by the condenser lens 5, its beam diameter is limited by thebeam limiting aperture 6, and the resultant beam is condensed by theobjective lens 8. The condensed beam is emitted to scan the surface ofthe sample 9 on the sample stage 10.

Secondary particles released from the sample are detected by thesecondary particle detector 11. A signal from the secondary particledetector 11 is subjected to brightness modulation, and the resultantsignal is sent to the computer processor 99. The computer processor 99generates a scan ion microscope image and displays it on the imagedisplay unit. In such a manner, high-resolution observation on thesample surface can be realized.

FIG. 3 shows an example of the configuration of the gas field ion source1 and its cooling mechanism 4 in the ion microscope according to theinvention illustrated in FIG. 1. The gas field ion source 1 and avibration preventing mechanism 70 of an emitter tip will be described indetail with reference to FIG. 4. The cooling mechanism 4 will bedescribed here. In the example, as the cooling mechanism 4 of the gasfield ion source 1, a cooling mechanism obtained by combining theGM-type refrigerator 40 and a helium gas pot 43 is used. The centeraxial line of the GM-type refrigerator is disposed in parallel to theoptical axis of the ion beam irradiation system passing an emitter tip21 of the ion microscope. With the configuration, both improvement inconvergence of the ion beam and improvement in the refrigeratingfunction can be satisfied.

The GM-type refrigerator 40 has a body 41, a first cooling stage 42A,and a second cooling stage 42B. The body 41 is supported by the supportpillar 103. The first and second cooling stages 42A and 42B are hangedfrom the body 41.

The outside diameter of the first cooling stage 42A is larger than thatof the second cooling stage 42B. The refrigeration capacity of the firstcooling stage 42A is about 5 W, and that of the second cooling stage 42Bis about 0.2 W. The first cooling stage 42A is cooled to about 50K. Thesecond cooling stage 42B can be cooled to 4K.

The upper end part of the first cooling stage 42A is surrounded by abellows 69. The lower end part of the first cooling stage 42A and thesecond cooling stage 42B are covered with the gas-sealing pot 43. Thepot 43 has a part 43A having a large diameter and configured to surroundthe first cooling stage 42A and a part 43B having a small diameter andconfigured to surround the second cooling stage 42B. The pot 43 issupported by the support pillar 104. The support pillar 104 is supportedby the base plate 18 as shown in FIG. 1.

Each of the bellows 69 and the pot 43 has a sealed structure filled withhelium gas 46 as a heat conduction medium. The two cooling stages 42Aand 42B are surrounded by the helium gas 46 but are in non-contact withthe pot 43. In place of the helium gas, neon gas or hydrogen may beused.

In the GM-type refrigerator 40, the first cooling stage 42A is cooled toabout 50K. Consequently, the helium gas 46 in the periphery of the firstcooling stage 42A is cooled to about 70K. The second cooling stage 42Bis cooled to 4K. The helium gas 46 in the periphery of the secondcooling stage 42B is cooled to about 6K. In such a manner, the lower endof the pot 43 is cooled to about 6K.

The vibration of the body 41 of the GM-type refrigerator 40 istransmitted to the support pillar 103 and the two cooling stages 42A and42B. The vibration transmitted to the cooling stages 42A and 42B isattenuated in the helium gas 46. Even when the cooling stages 42A and42B in the GM-type refrigerator vibrate, due to the existence of thehelium gas in the middle, heat is conducted but mechanical vibrationattenuates. Consequently, the vibration does not easily propagate to thesealed pot 43 which is cooled in the first and second stages 41 and 42.Particularly, vibration of high frequency is not easily transmitted.There is, consequently, an effect such that the mechanical vibration ofthe pot 43 is reduced much more than that of the cooling stages 42A and42B of the GM-type refrigerator.

As described with reference to FIG. 1, the vibration of the compressor16 is transmitted to the device stand 17 via the floor 20 and isprevented from being transmitted to the base plate 18 by the vibrationpreventing mechanism 19. Therefore, the vibration of the compressor 16is not transmitted to the support pillar 104 and the pot 43.

The lower end of the pot 43 is connected to a cooling conduction rod 53made of copper and having high thermal conductivity. A gas supply pipe25 is provided in the cooling conduction rod 53. The cooling conductionrod 53 is covered with a cooling conduction pipe 57 made of copper.

In the example, a not-shown shield for reducing thermal radiation isconnected to the part 43A having a large diameter of the pot 43, and theradiation shield is connected to the cooling conduction pipe 57 made ofcopper. Therefore, the cooling conduction rod 53 and the coolingconduction pipe 57 are always held at the same temperature as that ofthe pot 43.

Although the GM-type refrigerator 40 is used in the example, in place ofit, a pulse tube refrigerator or Stirling refrigerator may be used.Although the refrigerator has two cooling stages in the example, therefrigerator may have a single cooling stage. The number of coolingstages is not limited.

Referring to FIG. 4, an example of the configuration of the gas fieldion source, the emitter tip vibration preventing mechanism 70, and theperiphery of the ion microscope according to the invention will bedescribed in detail. FIG. 5 is a cross section taken line A-B of FIG. 4.The gas field ion source of the example has the emitter tip 21, anemitter base mount 64, an extraction electrode 24, and an electrostaticlens 59. The extraction electrode 24 has a hole through which an ionbeam passes. In the example, the electrostatic lens 59 has threeelectrodes each having a center hole. The emitter tip 21 is disposed soas to be opposed to the extraction electrode 24.

Below the electrostatic lens 59, a scanning deflection electrode 301, anaperture grill 302, a shutter 303, and a secondary particle detector 305are provided. An ion beam passes along a center line 306 of the ionirradiation system.

The emitter tip 21 is hanged from an upper flange 51, and the supportpart of the emitter tip 21 has a movable structure. On the other hand,the extraction electrode 24 is fixedly attached to a vacuum vessel 68.The vacuum vessel 68 is an upper structure of the column shown in FIG.1.

The emitter tip 21 is supported by a sapphire base 52. The sapphire base52 is connected to the cooling conduction rod 53 via a copper strandedwire 54. The extraction electrode 24 is supported by a sapphire base 55.The sapphire base 55 is connected to the cooling conduction rod 53 via acopper stranded wire 56. Therefore, a heat transfer path is constructedby the emitter tip 21, the sapphire base 52, the copper stranded wire54, the cooling conduction rod 53, and the pot 43. Similarly, a heattransfer path is constructed by the extraction electrode 24, thesapphire base 55, the copper stranded wire 56, the cooling conductionrod 53, and the pot 43.

The cooling mechanism has cold generating means which generates cold bymaking first high-pressure gas generated by the compressor unit expand,and a cooling mechanism for cooling the emitter tip 21 as a member to becooled by a second gas as helium gas in the pot 43 which is cooled bythe cold of the cold generating means.

A radiation shield 58 is provided so as to surround the emitter tip 21and the extraction electrode 24. The radiation shield 58 reduces thermalinflow by thermal radiation to the extraction electrode 24 and theionization chamber. The radiation shield 58 is connected to the coolingconduction pipe 57. An electrode 60 closest to the extraction electrode24 among three electrodes of the electrostatic lens 59 is connected tothe radiation shield 58. A heat transfer path is constructed by theelectrode 60, the radiation shield 58, the cooling conduction pipe 57,the radiation shield, and the pot 43.

In the example, the sapphire bases 52 and 55 and the cooling conductionrod 53 are connected via deformable copper stranded wires 54 and 56. Thecopper stranded wire 54 has the function of holding the heat transferpath made by the emitter tip 21, the sapphire base 52, and the coolingconduction rod 53 even if the position of the emitter tip 21 displaces.Further, the copper stranded wire 54 having high flexibility preventsthe high-frequency vibration from being transmitted to the sapphire base52 and the emitter tip 21 via the cooling conduction rod 53. The copperstranded wire 56 prevents the high-frequency vibration from beingtransmitted to the sapphire base 55 and the extraction electrode 24 viathe cooling conduction rod 53. The copper stranded wire 54 as a heattransfer member is not limited to copper but a flexible member which hashigh thermal conductivity and does not easily transmit vibration, suchas a silver stranded wire may also be employed.

The device is, as already described, configuration so that vibrationfrom the floor and the vibration of the refrigerator are attenuated andtransmitted to the emitter tip. However, to maximally use thecharacteristics of the ion source, the following vibration preventingmechanism is also provided. Specifically, a diamagnetic block 71 isinserted in a part of the emitter base mount 64 connected to thesapphire base 52, and a ring-shaped electromagnet 72 is disposed aroundthe diamagnetic block 71. Preferably, the diamagnetic block 71 is madeof a substance which exhibits diamagnetism at extremely low temperature,for example, Er₃Ni. The ring-shaped electromagnet is fixed to the vacuumvessel 68 by a supporting member 73. When the electromagnet 72 isallowed to operate, repulsion force works as a magnetic interaction workbetween the electromagnet 72 and the diamagnetic block 71, and a forceof fixing the diamagnetic block 71 to the electromagnet works. Theposition of the ring-shaped electromagnet 72 can be adjusted byoperating a knob 74 from the outside of the vacuum vessel, and theemitter tip position can be adjusted. The diamagnetic block 71 and thering-shaped electromagnet 72 are not in contact with each other, andheat is not transmitted to the emitter tip by conduction. Consequently,the emitter tip 21 is held at extremely low temperature, and there is aneffect such that ion current from the emitter tip can be increased.

In place of the electromagnet of the embodiment, a permanent magnet maybe disposed around the diamagnetic block.

When the electromagnet of the example is constructed by asuperconducting coil, the emitter tip is firmly fixed by a strongermagnetic field. In this case, the superconducting block is connected tothe radiation shield 58 which is cooled, and the superconducting blockis cooled to a superconducting state. Further, for the supporting member73, a material having low thermal conductivity, for example, fiber-glassreinforced plastic, a PEEK material, or the like is used. By using sucha material, transmission of heat to the superconductor material isreduced, and a superconducting state is maintained.

In the above example, the force of fixing the emitter tip works in adirection perpendicular to the ion beam extraction direction. In thiscase, an ion beam device particularly with improved resolution of an ionimage is realized. Alternately, the diamagnetic block 71 and theelectromagnet 72 may be disposed as shown in FIG. 5 so that the force offixing the emitter tip 21 works in the direction parallel to the ionbeam extraction direction. In this case, the distance between theemitter tip and the extraction electrode is maintained constant, and aneffect such that the stable ion beam current is obtained is produced. Bycombining both of the cases, firmer fixation of the emitter tip isrealized, and the effects of both of the cases can be realized.

In the embodiment, extremely low temperature of the emitter tip isrealized, the gas field ion source capable of obtaining an ion beam oflarger current is provided and, moreover, an effect such that the ionmicroscope realizing high-resolution observation is provided isobtained.

Although the extraction electrode is fixed to the vacuum vessel in thegas field ion source of the example, the emitter tip is movable withrespect to the extraction electrode. Consequently, the positionadjustment of the emitter tip with respect to the hole of the extractionelectrode and the axis adjustment of the emitter tip with respect to theoptical system can be performed so that a fine ion beam can be formed.

The emitter base mount in the specification denotes a member or a partof the member for supporting the emitter tip from the vacuum vessel. Theterm “non-contact” in the case of fixing the emitter base mount in anon-contact manner means that a member which is in contact is not alwaysnecessary to generate the fixing force. Even when there is a memberwhich is in contact for the purpose of, for example, voltage supply orconnection of a wire, not the purpose of the fixing force, the state isdefined as “non-contact”.

The axis adjustment of the emitter tip will be described. By moving theshutter 302, a hole provided in the shutter 302 is deviated from thecenter axial line 306 of the ion beam irradiation system. The ion beam14 generated by the emitter tip 21 passes through the electrostatic lens59, the scanning deflection electrode 301 and, further, a hole in theaperture grill 302, and collides with the shutter 302. From the shutter302, secondary particles 304 such as secondary electrons are generated.The secondary particles 304 are detected by the secondary particledetector 304, and a secondary particle image can be obtained. Byproviding small projections in the upper part of the shutter 302, an ionradiation pattern of the emitter tip can be observed in the secondaryparticle image. An ion radiation pattern can also be observed by formingfine holes, mechanically scanning the aperture grill 302 in twodirections perpendicular to the ion beam, and detecting secondaryparticles generated when another shutter plate is irradiated with theion beam passed through the aperture grill 302.

While observing the ion radiation pattern in such a manner, the positionand angle of the emitter tip are adjusted. After the axis adjustment ofthe emitter tip, the shutter 302 is moved. With the movement, the ionbeam passes through the hole in the shutter 302. In addition, a variableradiation pattern observation mechanism 303 can be used. Specifically,the movable radiation pattern observation mechanism 303 is moved todeviate the hole formed in the movable radiation pattern observationmechanism 303 from the center axis line 306 of the ion beam radiationsystem. In the movable radiation pattern observation mechanism 303, anion image detector 307 made by a microchannel plate and a fluorescentplate is disposed. An image of the fluorescent plate can be observed bya mirror disposed below the ion image detector 307. That is, the ionbeam radiation direction and the radiation pattern can be observed.After completion of the observation, the hole provided in the movableradiation pattern observation mechanism 303 is returned to the centeraxis line 306 of the ion beam radiation system to make the ion beampass.

With reference to FIG. 7, the configuration of the gas field ion sourceof the ion microscope according to the present invention will bedescribed more specifically. Another example of the above-describedmethod of fixing the emitter tip 21 in a non-contact manner will bedescribed. The gas field ion source of the example has the emitter tip21, a pair of filaments 22, a filament mount 23, a supporting rod 26,and the emitter base mount 64. The emitter tip 21 is fixed to thefilaments 22. The filaments 22 are fixed to the supporting rod 26. Thesupporting rod 26 is supported by the filament mount 23. The filamentmount 23 is fixed to the emitter base mount 64. The emitter base mount64 is attached to the upper flange 51 as shown in FIG. 4. The emitterbase mount 64 and the radiation shield 58 or the vacuum vessel 68 areconnected by a bellows 61.

As already described, the device is configuration so that vibration fromthe floor and the vibration of the refrigerator are not transmitted tothe emitter tip. However, to maximally use the characteristics of theion source, the following vibration preventing mechanism is alsoprovided. Specifically, a superconductor block 75 is inserted in a partof the emitter base mount 64 connected to the sapphire base 52, and thering-shaped electromagnet 72 is disposed around the semiconductor block75. The ring-shaped electromagnet is fixed to the vacuum vessel 68 bythe supporting member 73. The position of the ring-shaped electromagnet72 can be adjusted by operating the knob 74 from the outside of thevacuum vessel.

The gas field ion source of the example further includes the extractionelectrode 24, a cylindrical-shape resistive heater 30, a cylindricalside wall 28, and a top plate 29. The extraction electrode 24 has a hole27 which is disposed so as to be opposed to the emitter tip 21 andthrough which the ion beam 14 passes. An insulating material 63 isconnected to the top plate 29. A bellow 62 is attached between theinsulating material 63 and the filament mount 23.

The side wall 28 and the top plate 29 surround the emitter tip 21. Thespace surrounded by the extraction electrode 24, the side wall 28, thebellows 62, the insulating material 63, and the filaments 23 is calledan ionization chamber 15.

To the ionization chamber 15, the gas supply pipe 25 is connected. Bythe gas supply pipe 25, an ion material gas (ionizable gas) is suppliedto the emitter tip 21. The ion material gas (ionizable gas) is helium orhydrogen.

The ionization chamber 15 is closed except for the hole 27 in theextraction electrode 24 and the gas supply pipe 25. The gas suppliedinto the ionization chamber via the gas supply pipe 25 is not leakedfrom the area other then the hole 27 in the extraction electrode 24 andthe gas supply pipe 25. By sufficiently reducing the diameter of thehole 27 in the extraction electrode 24, high airtightness and highsealing performance can be held in the ionization chamber. The diameterof the hole 27 in the extraction electrode 24 is, for example, 0.2 mm orless. Consequently, when the ionizable gas is supplied from the gassupply pipe 25 to the ionization chamber 15, the gas pressure in theionization chamber 15 becomes higher than that in the vacuum vessel byat least one digit. The ratio that the ion beam collides with the gas invacuum and is neutralized is therefore reduced, and the ion beam oflarge current can be generated. Even when a hole of conductance smallerthan that of the hole in the extraction electrode is formed in theionization chamber, the effects of the present invention are not lost.

The resistive heater 30 is used to perform degasifying process on theextraction electrode 24, the side wall 28, and the like. By heating theextraction electrode 24, the side wall 28, and the like, the degasifyingis accelerated. The resistive heater 30 is disposed on the outside ofthe ionization chamber 15. Therefore, even if the resistive heateritself performs the degasifying operation, it is performed on theoutside of the ionization chamber, so that the inside of the ionizationchamber can be made under high vacuum.

Although the resistive heater is used for the degasifying process in theexample, in place of the resistive heater, a lamp for heating may beused. Since a lamp for heating can heat the extraction electrode 24 in anon-contact manner, the peripheral structure of the extraction electrodecan be simplified. Further, since it is unnecessary to apply highvoltage in the lamp for heating, the structure of the power source ofthe lamp for heating is simple. Further, in place of using the resistiveheater, an inactive gas of high temperature may be supplied via the gassupply pipe 25 to heat the extraction electrode, the side wall, and thelike, and perform the degasifying process. In this case, a gas heatingmechanism can be set to ground potential. Further, the peripheralstructure of the extraction electrode becomes simple, and a wire and apower source are unnecessary.

By the resistive heater attached to the sample chamber 3 and the pump 13for evacuating the sample chamber, the sample chamber 3 and the pump 13for evacuating the sample chamber may be heated to about 200° C., andthe degree of vacuum in the sample chamber 3 may be set to 10⁻⁷ Pa atthe maximum. By the operation, when a sample is irradiated with an ionbeam, the surface of the sample is avoided from being contaminated, andthe surface of the sample can be observed excellently. In theconventional technique, when the surface of a sample is irradiated witha beam of helium ion or hydrogen ion, since growth of deposition bycontamination is fast, there is the case that observation of the samplesurface becomes difficult. Consequently, the sample chamber 3 and thepump 13 for evacuating the sample chamber are subjected to heatingprocess in the vacuum state, and the hydrocarbon-based residual gas inthe vacuum of the sample chamber 3 is reduced to a very small amount. Asa result, the most surface of the sample can be observed with highresolution.

Next, the operation of the gas field ion source of the example will bedescribed. The vacuum vessel is evacuated by the ion source evacuationpump 12. By the resistive heater 30, process of degasifying theextraction electrode 24, the side wall 28, and the top plate 29 isperformed. Specifically, by heating the extraction electrode 24, theside wall 28, and the top plate 29, degasifying is performed.Simultaneously, another resistive heater may be disposed on the outsideof the vacuum vessel to heat the vacuum vessel. With the configuration,the degree of vacuum in the vacuum vessel improves, and the temperatureof the residual gas decreases. By the operation, time stability of ionemission current can be improved.

After completion of the degasifying process, heating by the resistiveheater 30 is stopped. After lapse of sufficient time, the refrigeratoris operated. By the operation, the emitter tip 21, the extractionelectrode 24, the radiation shield 58, and the like are cooled. Next,ionization gas is introduced by the gas supply pipe 25 into theionization chamber 15. The ionization gas is helium or hydrogen.Description will be given on assumption that the ionization gas ishelium. As described above, the degree of vacuum in the ionizationchamber is high. Therefore, the ratio that the ion beam generated by theemitter tip 21 collides with the residual gas in the ionization chamberand is neutralized decreases. Consequently, a high-current ion beam canbe generated. The number of helium gas molecules of high temperaturewhich collide with the extraction electrode decreases. It can decreasethe cooling temperature of the emitter tip and the extraction electrode.Therefore, the high-current ion beam can be emitted to a sample.

Next, voltage is applied across the emitter tip 21 and the extractionelectrode 24. An intense electric field is generated at the end of theemitter tip. Most of helium supplied from the gas supply pipe 25 ispulled to the emitter tip face by the intense electric field. The heliumreaches near the end of the emitter tip where the electric field istensest. The helium ionizes and a helium ion beam is generated. Thehelium ion beam is led to the ion beam radiation system via the hole 27in the extraction electrode 24.

The emitter tip fixing method, that is, a vibration preventing mechanismusing a superconductor block in a part of the emitter tip mountconnected to the sapphire base 52 will be described later.

Next, the structure of the emitter tip 21 and the method of producingthe same will be described. First, a tungsten wire having a diameter ofabout 100 to 400 μm and whose axial direction <111> is prepared, and itstip is sharpened. As a result, the emitter tip whose end has a radius ofcurvature of about 10 nm is obtained. At the end of the emitter tip,platinum is vacuum-deposited in another vacuum vessel. Next, theplatinum atom is moved to the end of the emitter tip in high-temperatureheating. As a result, a pyramid-shaped structure in nanometer order bythe platinum atom is formed. The structure will be called anano-pyramid. The nano-pyramid typically has one atom at its end, alayer of three or six atoms below the one atom, and a layer of ten ormore atoms below the layer.

Although the thin wire of tungsten is used in the example, a thin wireof molybdenum can also be used. Although coating of platinum is used inthe example, coating of iridium, rhenium, osmium, palladium, rhodium, orthe like can also be used.

In the case of using helium as the ionization gas, it is important thatthe evaporation intensity of a metal is higher than the electric fieldintensity at which helium ionizes. Therefore, the coating of platinum,rhenium, osmium, or iridium is preferable. In the case of using hydrogenas the ionization gas, coating of platinum, rhenium, osmium, palladium,rhodium, or iridium is preferable. Although the coating of any of themetals can be formed by vacuum deposition, it can also be formed byplating in a solution.

As another method of forming the nano-pyramid at the end of the emittertip, field evaporation in vacuum, ion beam radiation, or the like mayalso be employed. By any of such methods, the tungsten atom ormolybdenum atom pyramid can be formed at the end of the tungsten wire ormolybdenum wire. For example, in the case of using a tungsten wire of<111>, the end is constructed by three tungsten atoms.

As described above, the characteristic of the emitter tip 21 of the gasfield ion source according to the present invention is the nano-pyramid.By adjusting the electric field intensity formed at the end of theemitter tip 21, a helium ion can be generated near the one atom at theend of the emitter tip. Therefore, a region from which an ion isemitted, that is, an ion light source is an extremely narrow regionwhich is a nanometer or less. By generating an ion from the very limitedregion as described above, the beam diameter of 1 nm or less can berealized. Consequently, the unit area of the ion source and the currentvalue per unit solid angle becomes large. This is an importantcharacteristic to obtain a high-current ion beam having a very smalldiameter on a sample.

Particularly, in the case of depositing platinum on tungsten, thenano-pyramid structure in which one atom exists at the end is stablyformed. In this case, the generation place of the helium ion isconcentrated near the one atom at the end. In the case of three atoms atthe end of tungsten <111>, the generation place of the helium ion isdispersed to places near the three atoms. Therefore, the current emittedfrom the unit area/unit solid angle in the ion source having thenano-pyramid structure of platinum in which the helium gas isconcentratedly supplied to the one atom is larger. That is, the emittertip in which platinum is deposited on tungsten produces effects suchthat the beam diameter on the sample of the ion microscope is reduced,and current is increased. Even if rhenium, osmium, iridium, palladium,rhodium, or the like is used, in the case where a nano-pyramid havingone atom at its end is formed, current emitted from the unit area/unitsolid angle can also be increased. It is therefore preferable to reducethe diameter of a beam on a sample of the ion microscope or increasecurrent.

FIG. 8 shows an ion beam device related to reduction of adhesion ofdesorption gas from a beam limiting aperture to the emitter tip. Asalready described, the ion beam 14 generated by the gas field ion source1 is condensed by the condenser lens 5, the beam diameter is regulatedby the beam limiting aperture 6, and the resultant beam is focused bythe objective lens 8. The focused beam is emitted to scan the sample 9on the sample stage 10. For the conventional ion microscope, asufficient measure is not employed from the viewpoints of adhesion ofgas generated when an ion beam is emitted to a beam limiting aperture orthe like to the emitter tip, and deterioration in stability of ion beamcurrent. That is, the inventors of the present invention have found aproblem such that desorption molecules generated when the beam limitingaperture or the like is irradiated with an ion beam are adhered to theend of the emitter tip and it makes the ion beam current unstable.Specifically, when helium which becomes close to the molecules adheredto the end of the emitter tip is ionized, supply of helium to the tip ofthe nano-pyramid is reduced, and the ion beam current decreases. Thatis, the existence of impurity gas makes the ion beam current unstable.

When the beam limiting aperture is a hole formed in a plate 500, in thepresent invention, a radiation direction 501 of an ion beam and a normal502 to the plate have a tilt relation as shown in FIG. 8. With theconfiguration, most of desorption molecules 503 generated when the beamlimiting aperture 500 is irradiated with the ion beam 14 do not flytoward the emitter tip 21, and molecules adhered to the emitter tip 21dramatically decrease. Therefore, the ion beam device with a stable ionbeam current which enables sample observation having no brightnessunevenness in an observation image is provided. In particular, it hasbeen found that when the angle between the radiation direction of theion beam and the normal of the plate is set to 45 degrees or larger,impurity gas molecules are hardly adhered to the emitter tip, and theion beam current is stabilized.

The inventors of the present invention have also found that it isparticularly effective when the degree of vacuum in the vacuum vesselcontaining the beam limiting aperture is set to 10⁻⁷ Pa or less from theviewpoint that the impurity gas adhered to the beam limiting aperturedesorbs. The vacuum vessel containing the beam limiting aperture has abaking heater 504 which can be heated to about 200° C. By baking thevacuum vessel while performing evacuation, the degree of vacuum can beset to 10⁻⁷ Pa or less. It is more effective that the plate 500 of thebeam limiting aperture is cleaned with plasma to a state where adheredmolecules are reduced. A vacuum pump 505 for exhausting the vacuumvessel containing the beam limiting aperture is preferably, a noblepump, an ion pump, a non-evaporable Getter pump, or the like.Particularly, an evacuation system in which a turbo-molecular pump or arotary pump is not operated produces an effect such that vibration ofthe emitter tip is reduced and an image of high resolution is obtained.

Before an element having light mass such as helium or hydrogen isextracted as an ion beam, an element having heavy mass such as neon,argon, krypton, xenon, or the like is extracted as an ion beam, and theextracted beam is emitted to the beam limiting aperture. The inventorsof the present invention have found that, in such a manner, most ofimpurities adhered to the beam limiting aperture desorbs and, in thecase of emitting an element having light mass such as helium or hydrogenas an ion beam, the impurity gas desorbed from the beam limitingaperture decreases. That is, the ion beam device with a stable ion beamcurrent which enables sample observation having no brightness unevennessin an observation image is provided.

Next, an example of paying attention to a phenomenon that the impurityin the ionization gas supplied to the periphery of the emitter tip makesthe ion current unstable will be described with reference to FIG. 9. Thepurity of gas for supplying the ionization gas of the ion source ishigh, and the concentration of the impurity is a 1/10⁵ level. Theinventors of the present invention have found a problem such that asmall amount of impurity gas contained adheres to the end of the emittertip and it makes the ion beam current unstable. Consequently, in theembodiment, as shown in FIG. 9, a buffer tank 511 for ion sourcepurification containing a non-evaporable Getter material is provided.Around the buffer tank, a baking heater 512 capable of heating theentire buffer tank to about 200° C. and an activation heater 514 capableof heating a non-evaporable Getter material 513 to 500° C. are provided.An on-off valve 516 is provided between the buffer tank 511 and an ionmaterial gas cylinder 515, and an off-off valve 518 is provided betweenthe buffer tank 511 and a vacuum pump 517.

Next, a way of using the buffer tank for ion source purification will bedescribed. First, the valve 518 between the buffer tank 511 and thevacuum pump 517 is opened to evacuate the buffer tank 511. After that,the entire buffer tank is heated at about 200° C. and the impurity gasadsorbed on the wall in the tank is exhausted.

Immediately after completion of heating, the non-evaporable Gettermaterial 513 is heated to 500° C. The non-evaporable Getter material 513is activated and gas molecules are adsorbed. In the case of using theion material gas as inactive gas such as helium or argon, the gas is notadsorbed. Next, the valve between the buffer tank and the vacuum pump isclosed and the valve 516 between the buffer tank and the cylinder gas515 is opened. After a predetermined amount of the ion material gas isstored in the buffer tank, the valve 516 is closed. The impurity gascontained in the ion source material is adsorbed to the non-evaporableGetter material, and the ion source material gas is purified. The flowrate of the gas is controlled by a flow rate adjustment valve, and theresultant gas is introduced into the ion source. To be specific, the gasis introduced to the periphery of the emitter tip 21 in the ionizationchamber. The impurity gas molecules adhered to the emitter tip 21decrease dramatically, the ion beam current becomes stable, and an ionbeam device which enables sample observation having no brightnessunevenness in an observation image is provided.

In FIG. 7, the non-evaporable Getter material is used for the ionizationchamber. In the embodiment, a Getter material 520 is disposed on thewall with which the gas released from the ion material gas supply pipe25 collides. The heating heater 30 is provided for the outer wall of theionization chamber. Before introduction of the ionization gas, thenon-evaporable Getter material 520 is heated and activated. The emittertip is provided with a contamination preventing cover 521 so that theimpurity gas released from the non-evaporable Getter material goesdirectly to the emitter tip 21. The ion source is cooled to very lowtemperature and, after that, the ionization gas is supplied from theionization material gas supply pipe 25. In such a manner, the impuritygas molecules adhered to the emitter tip decrease dramatically, the ionbeam current becomes stable, and the ion beam device which enablessample observation having no brightness unevenness in an observationimage is provided.

Similarly, the inventors have found a problem such that the impurity gasflowing from the sample chamber vacuum vessel into the ion source vacuumvessel is adhered to the end of the emitter tip and makes the ion beamcurrent unstable. The degree of vacuum is set to 10⁻⁷ Pa by a noblepump, an ion pump, and a non-evaporable Getter pump, and the impuritygas flowing in the ion source vacuum vessel is reduced as much aspossible. As a result, the impurity gas molecules adhered to the emittertip decrease dramatically, the ion beam current becomes stable, and theion beam device which enables sample observation having no brightnessunevenness in an observation image is provided.

The ion source is characterized by using ions released from theneighborhood of one atom at the end of the nano-pyramid. That is, theregion from which the ion is emitted is narrow, and the ion light sourceis equal to a nanometer or less. Consequently, when the ion light sourceis focused on the sample at the same magnification and the reductionratio is set to about 1/2, the characteristic of the ion source can beutilized maximally. In the conventional gallium liquid metal ion source,the dimension of the ion light source is estimated as about 50 nm.Therefore, to realize the beam diameter of 5 nm on a sample, thereduction ratio has to be set to 1/10 or less. In this case, thevibration of the emitter tip in the ion source is reduced to 1/10 orless on a sample. For example, even when the emitter tip vibrates by 10nm, the vibration of the beam spot on a sample is 1 nm or less.

Therefore, the influence of the vibration of the emitter tip on the beamdiameter of 5 nm is light. In the example, the reduction ratio isrelatively large and is about 1 to 1/2. Accordingly, in the case wherethe reduction ratio is 1/2, the vibration of 10 nm at the emitter tipbecomes the vibration of 5 nm on the sample, and the vibration of thesample for the beam diameter is large. That is, to realize resolutionof, for example, 0.2 nm, the vibration of the emitter tip has to be setto 0.1 nm or less at the maximum. The conventional ion source is notalways satisfactory from the viewpoint of prevention of vibration at theend of the emitter tip.

To address the problem, in the present invention, the vibrationpreventing mechanism is provided as shown in FIG. 1. That is, thevibration preventing mechanism 19 prevents the vibration of therefrigerator 40 and the compressor 16 from being easily transmitted tothe gas field ion source 1, the ion beam irradiation system column 2,and the sample chamber 3. The vibration of the compressor 16 is noteasily transmitted to the pot 43 and the sample stage 10.

Further, as shown in FIG. 7, in the present invention, a vibrationpreventing mechanism using the superconductor block 75 is provided in apart of the emitter base mount 64 connected to the sapphire base 52. Thering-shaped electromagnet 72 is disposed around the superconductor blockand is fixed to the vacuum vessel by the supporting member 73. First,the electromagnet is operated at a temperature at which asuperconducting state is not obtained. As the emitter tip is cooled, thesuperconductor block is set to the superconducting state. Eventually, aso-called pinning effect of pinning the magnetic field from theelectromagnet appears in the superconductor block. The superconductorblock 75 and the ring-shaped electromagnet 72 are fixed in a non-contactmanner, and vibration of the emitter tip attached to the end of thesuperconductor block 75 is prevented. The position of the ring-shapedelectromagnet can be adjusted from the outside of the vacuum vessel, andthe position of the emitter tip can be adjusted. The superconductorblock and the ring-shaped electromagnet are not in contact with eachother, and heat is not transmitted to the emitter tip by conduction.Consequently, an effect such that the emitter tip is maintained atextremely low temperature, and current from the emitter tip can beincreased.

When the electromagnet of the present invention is constructed by asuperconductor coil, the emitter tip is firmly fixed by a strongermagnetic field. In place of the ring-shaped electromagnet, a permanentmagnet may be disposed around the superconductor block.

A plurality of electromagnets may be disposed around the superconductorblock 75. By controlling the magnetic field intensity of the pluralityof electromagnets, the position of the emitter tip base mount can becontrolled.

As described above, according to the present invention, by generating anion beam having a very small diameter and preventing vibration of theemitter tip, high-resolution observation of a sample surface can berealized. Since the air sealing in the ionization chamber is high in theion source and the degree of vacuum is high on the outside of theionization chamber, the ratio that the ion beam collides with gas in thevacuum and is neutralized is low. Therefore, an effect such that asample can be irradiated with a high-current ion beam is produced. Thenumber of helium gas molecules of high temperature which collide withthe extraction electrode decreases, and the cooling temperature of theemitter tip and the extraction electrode can be decreased, and an effectsuch that a sample can be irradiated with a high-current ion beam isproduced.

In the case where the nano-pyramid is damaged by an unexpected dischargephenomenon or the like, the emitter tip is heated for about 30 minutes(about 1,000° C.). By the operation, the nano-pyramid can be reproduced.That is, the emitter tip can be easily repaired. Consequently, apractical ion microscope can be realized.

The distance between the tip of the objective lens 8 and the surface ofthe sample 9 is called a work distance. When the work distance is set toa value less than 2 mm in the ion beam device, the resolution becomesless than 0.2 nm, and the super-resolution is realized. Since an ion ofgallium or the like is used conventionally, there is a concern such thatsputter particles from the sample contaminate the objective lens and thenormal operation is disturbed. The ion microscope according to thepresent invention has the reduced concern and can realize thesuper-resolution.

In the gas field ion source and the ion beam device according to thepresent invention as described above, the vibration from the coolingmechanism is not easily transmitted to the emitter tip. Since themechanism of fixing the emitter base mount is provided, the vibration ofthe emitter tip is prevented, and high-resolution observation is madepossible.

Further, in the gas field ion source of the present invention, bysufficiently reducing the hole 27 in the extraction electrode 24, thesealing performance of the ionization chamber increases, and the highgas pressure in the ionization chamber can be realized. Consequently,high-current ion emission is realized.

In the gas field ion source of the present invention, the heat transferpath extending from the cooling mechanism 4 to the emitter tip 21 isprovided, so that extremely low temperature of the emitter can berealized. Consequently, a high-current ion beam is obtained. In the gasfield ion source of the invention, the extraction electrode has a fixedstructure, the emitter tip has a movable structure, and the emitter tipand the extraction electrode are connected to each other via adeformable material. Thus, easier adjustment of the axis of the emittertip and the higher current of ions can be realized.

With reference to FIG. 10, a second example of the ion microscopeaccording to the present invention will be described. The ion microscopeof the second example is different from that of the second example withrespect to the configuration of the cooling mechanism 4 for the gasfield ion source 1. The cooling mechanism 4 will now be described. Thecooling mechanism 4 of the second example has a vacuum chamber 81 and acooling tank 82. The vacuum chamber 81 is constructed by a vacuum vesselhaving therein a cooling tank 82. The vacuum chamber 81 and the coolingtank 82 are not in contact with each other. Therefore, vibration andheat are hardly transmitted between the vacuum chamber 81 and thecooling tank 82.

The cooling tank 82 has an evacuation port 83. The evacuation port 83 isconnected to a not-shown vacuum pump. To the cooling tank 82, thecooling conduction rod 53 made of copper is connected in a mannersimilar to the example 1 shown in FIG. 3. Like the cooling mechanismshown in FIGS. 3 and 4, also in the second example, a heat transfer pathis constructed by the emitter tip 21, the sapphire base 52, the copperstranded wire 54, the cooling conduction rod 53, and the cooling tank82. Similarly, a heat transfer path is constructed by the extractionelectrode 24, the sapphire base 55, the copper stranded wire 56, thecooling conduction rod 53, and the cooling tank 82. The copper strandedwire 54 has high thermal conductivity. The material is not limited tocopper but any member such as a silver stranded wire can be employed aslong as it has flexibility and does not easily transfer vibration.

First, liquid nitrogen is introduced into the cooling tank 82 toevacuate the inside of the cooling tank via the evacuation port 83. Itdecreases the temperature of the liquid nitrogen. The liquid nitrogensolidifies and becomes solid nitrogen 84.

In the example, after the liquid nitrogen solidifies completely, thevacuum pump connected to the evacuation port 83 is stopped, and an ionbeam is generated by the emitter tip 21. When the vacuum pump isstopped, no mechanical vibration of the vacuum pump occurs.

During generation of an ion beam, heat is transmitted via the heattransfer path connecting the emitter tip 21, the extraction electrode24, and the cooling tank 82. The solid nitrogen in the cooling tank 82sublimes or melts. In the example, to cool the emitter tip 21 and theextraction electrode 24, latent heat such as sublimation heat or meltingheat can be used.

Before all of the solid nitrogen becomes liquid and boiling starts, thevacuum pump connected to the evacuation port 83 is operated to evacuatethe cooling tank 82. By the operation, the temperature of the liquidnitrogen decreases and solidifies. After all of the liquid nitrogensolidifies, the vacuum pump connected to the evacuation port 83 isstopped. By repeating the operation, the temperature of nitrogen in thecooling tank 82 can be always maintained at around the melting point ofnitrogen. The temperature of the nitrogen in the cooling tank 82 isalways lower than the boiling point. Therefore, vibration caused byboiling of the liquid nitrogen does not occur. In such a manner, thecooling mechanism of the example does not make mechanical vibrationoccur. Consequently, high-resolution observation can be made.

In the example, to control the operation of the vacuum pump connected tothe evacuation port 83, the temperature of nitrogen in the cooling tank82 is measured. For example, when the temperature of nitrogen becomespredetermined temperature higher than the melting point, the operationof the vacuum pump connected to the evacuation port 83 is started. Whenthe temperature of nitrogen becomes predetermined temperature lower thanthe melting point, the operation of the vacuum pump connected to theevacuation port 83 is stopped. In place of the temperature of nitrogenin the cooling tank 82, the degree of vacuum may be measured and theoperation of the vacuum pump connected to the evacuation port 83 may becontrolled according to the measured degree of vacuum.

In the example, by evacuating the cooling tank 82, the liquid nitrogenin the cooling tank 82 is cooled. However, gas-phase nitrogen isexhausted, and nitrogen decreases with time. By using the refrigerator,the solid nitrogen in the cooling tank 82 may be cooled. As a result,decrease in nitrogen can be prevented. Preferably, during operation ofthe refrigerator, generation of an ion beam by the gas field ion source1 is stopped. That is, with the ion source of the embodiment, an ionmicroscope which realizes reduction in mechanical vibration and enableshigh-resolution observation is provided.

Over the device stand 17 mounted on the floor 20, the base plate 18 isdisposed via the vibration preventing mechanism 19. The gas field ionsource 1, the column 2, and the sample chamber 3 are supported by thebase plate 18.

The device stand 17 is provided with a supporting pillar 85. By thesupporting pillar 85, the evacuation port 83 of the cooling tank 82 issupported. The supporting pillar 85 and the vacuum chamber 81 areconnected to each other via a bellows 86. The base plate 18 is providedwith a supporting pillar 87. The vacuum chamber 81 is supported by thesupporting pillar 87 and is simultaneously hanged by the supportingpillar 85 via the bellows 86.

The bellows 86 reduces transmission of high-frequency vibration.Therefore, even when vibration from the floor 20 is transmitted to thesupporting pillar 85 via the device stand 17, it is reduced by thebellows 86. Therefore, the vibration from the floor 20 is hardlytransmitted to the vacuum chamber 81 via the supporting pillar 85. Thevibration from the floor 20 is transmitted to the device stand 17.However, the vibration from the floor 20 is hardly transmitted to thebase plate 18 by the vibration preventing mechanism 19. Therefore, thevibration from the floor 20 is hardly transmitted to the vacuum chamber81 via the supporting pillar 87.

As described above, in the example, the vibration from the floor 20 isnot transmitted to the vacuum chamber 81 and the cooling tank 82.Therefore, the vibration from the floor 20 is not transmitted to the gasfield ion source 1, the ion beam radiation system column 2, and thesample chamber 3 via the cooling mechanism 4.

In some conventional techniques, vibration of a tank which stores liquidnitrogen is considered. However, transmission of the vibration of thetank to the vacuum chamber and an influence of the vibration on an ionbeam are not sufficiently examined. According to the present invention,the vibration of the cooling tank 82 is not easily transmitted to thevacuum chamber 81. Since the vibration from the floor 20 via the vacuumchamber 81 and the cooling tank 82 is reduced, the high-resolution ionbeam microscope is provided.

Although nitrogen is charged in the cooling tank 82 in the example,neon, oxygen, argon, methane, hydrogen, or the like may be used exceptfor nitrogen. Particularly, in the case of using solid neon, lowtemperature which is suitable to make a high-current helium or hydrogenion beam can be realized.

FIG. 11 shows the emitter tip vibration preventing mechanism in theembodiment. In the embodiment, a vibration preventing mechanism in whicha plurality of permanent magnets 530 are buried is provided in a part ofthe emitter base mount 64. A superconductor block 531 is disposed aroundthe permanent magnets 530 and fixed to the ionization chamber side wall28. As the emitter tip, that is, the ionization chamber is cooled, thesuperconductor block 531 is set to a superconducting state. Eventually,a so-called pinning effect of pinning the magnetic field from theelectromagnet 530 appears in the superconductor block. Thesuperconductor block 531 and the permanent magnet 530 are fixed in anon-contact manner, and vibration of the emitter tip attached to the endof the emitter base mount 64 is prevented. Since the superconductorblock is connected to the ionization chamber side wall 28 of extremelylow temperature, the vibration preventing mechanism does not add a largeamount of heat to the emitter tip. Consequently, the emitter tip ismaintained at extremely low temperature, and there is an effect suchthat an ion beam current from the emitter tip can be increased.

In the embodiment, by burying the superconductor block in the emitterbase mount 64 and disposing a permanent magnet on the ionization chamberside wall 28, a similar effect is obtained.

Although not shown, a magnetic shield is disposed on the emitter tipmount 23 so that the magnetic field from the permanent magnet does notexert an influence on an ion beam orbit. As a result, both emitter tipvibration prevention and no influence on the orbit of the ion beam canbe realized.

As described above, in the gas field ion source and the ion beam deviceof the present invention, vibration from the cooling mechanism is noteasily transmitted to the emitter tip. Since the emitter base mountfixing mechanism is provided, vibration of the emitter tip is prevented,and high-resolution observation is realized.

With reference to FIG. 12, a third example of the ion microscopeaccording to the present invention will be described. The ion microscopeof the third example is different from that of the first example shownin FIG. 1 with respect to the configuration of the cooling mechanism 4for the gas field ion source 1. The cooling mechanism 4 will now bedescribed. The cooling mechanism 4 of the third example is of a heliumcirculation type.

The cooling mechanism 4 of the example cools helium gas as a refrigerantby using a GM-type refrigerator 401 and heat exchangers 402, 405, 410,and 414 and makes the gas circulate by a compressor unit 400. The heliumgas having 0.9 Mpa and a temperature of 300K at normal temperature whichis compressed by a compressor 403 flows in the heat exchanger 402 via apipe 409, exchanges heat with a low-temperature helium gas which isreturning and will be described later, and is cooled to a temperature ofabout 60K. The cooled helium gas is transported via a pipe 403 in aninsulated transfer tube 404 and flows in the heat exchanger 405 disposednear the gas field ion source 1. A heat conductor 406 thermallyintegrated with the heat exchanger 405 is cooled to temperature of about65K and cools the above-described radiation shield and the like. Theheated helium gas flows out from the heat exchange 405, flows, via thepipe 407, in the heat exchanger 409 thermally integrated with a firstcooling stage 408 in the GM-type refrigerator 401, is cooled totemperature of about 50K, and flows in the heat exchanger 410. Thehelium gas exchanges heat with a low-temperature helium gas which isreturning and will be described later, and is cooled to a temperature ofabout 15K. After that, the cooled gas flows in a heat exchanger 412which is thermally integrated with a second cooling stage 402 in theGM-type refrigerator 401, is cooled to temperature of about 9K, istransported via a pipe 413 in the transfer tube 404, flows in the heatexchanger 414 disposed near the gas field ion source 1, and cools thecooling conduction rod 53 as a heat conductor thermally connected to theheat exchanger 414 to a temperature of about 10K. The helium gas heatedby the heat exchanger 414 sequentially flows in the heat exchangers 410and 402 via a pipe 415, exchanges heat with the above-described heliumgas to a temperature of about 275K at almost normal temperature, and theresultant gas is collected by the compressor unit 400 via the pipe 415.The above-described low-temperature part is housed in a vacuuminsulation vessel 416 and, although not shown, is adiabaticallyconnected to the transfer tube 404. Although not shown, thelow-temperature part prevents heat invasion by radiation heat from aroom-temperature part by a radiation shield plate, a multilayerinsulation material, or the like in the vacuum insulation vessel 416.

The transfer tube 404 is firmly fixed by the floor 20 or a supportingmember 417 mounted on the floor 20. Although not shown, the pipes 403,407, 413, and 415 fixedly supported in the transfer tube 404 by a heatinsulating member made of glass fiber plastic as a heat insulatingmaterial having low thermal conductivity are also fixedly supported bythe floor 20. Near the gas field ion source 1, the transfer tube 404 isfixedly supported by the base plate 18. Similarly, although not shown,the pipes 403, 407, 413, and 415 fixedly supported in the transfer tube404 by a heat insulating member made of glass fiber plastic as a heatinsulating material having low thermal conductivity are also fixedlysupported by the base plate 18.

The cooling mechanism has cold generating means which generates cold bymaking first high-pressure gas generated by the compressor unit 16expand, and a cooling mechanism for performing cooling by the cold ofthe cold generating means and cooling a member to be cooled by a heliumgas as a second moving refrigerant which is circulated by the compressorunit 400.

The cooling conduction rod 53 is connected to the emitter tip 21 via thedeformable copper stranded wire 54 and the sapphire base. As a result,cooling of the emitter tip 21 is realized. In the embodiment, theGM-type refrigerator is a cause of vibrating the floor. However, the gasfield ion source 1, the ion beam irradiation system column 2, the vacuumsample chamber 3, and the like are mounted apart from the GMrefrigerator. Further, the pipes 403, 407, 413, and 415 coupled to theheat exchangers 405 and 414 mounted near the gas field ion source 1 arefirmly fixedly supported by the floor 20 and the base 18 which hardlyvibrate, and do not vibrate. Moreover, they are vibration-insulated fromthe floor, so that the system having an extremely little transmission ofmechanical vibration is obtained.

However, to maximally utilize the characteristic of the ion source, thevibration preventing mechanism as shown in FIG. 11 is provided.Permanent magnets are disposed in a plurality of places in the peripheryof the emitter base mount, and a superconductor block is disposed aroundthe permanent magnets. The superconductor block is fixed to theionization chamber side wall. In this case, the superconductor blockenters a superconducting state as the ionization chamber is cooled.

First, the emitter tip position is adjusted at a temperature at whichthe superconducting state is not obtained. As the emitter tip is cooled,the superconductor block is set to the superconducting state.Eventually, a so-called pinning effect of pinning the magnetic fieldfrom the permanent magnets appears in the superconductor block. Theemitter tip mount in which the permanent magnets are disposed is fixedin a non-contact manner, and vibration of the emitter tip attached tothe end of the emitter tip mount is prevented. Since the superconductorblock is connected to the ionization chamber side wall 28 of extremelylow temperature, the vibration preventing mechanism does not add a largeamount of heat to the emitter tip. Consequently, the emitter tip ismaintained at extremely low temperature, and there is an effect suchthat an ion beam current from the emitter tip can be increased. Bydisposing the superconductor block in the emitter base mount, disposingpermanent magnets around the superconductor block, and fixing thepermanent magnets to the ionization chamber side wall, a similar effectis obtained.

As described above, in the gas field ion source and the ion beam deviceof the present invention, vibration from the cooling mechanism is noteasily transmitted to the emitter tip. Since the emitter base mountfixing mechanism is provided, vibration of the emitter tip is prevented,and high-resolution observation is realized.

Further, the inventors of the present invention found out that sound ofthe compressor 16 or 400 makes the gas field ion source 1 vibrate and itdeteriorates the resolution. Consequently, in the example, a cover 417for spatially separating the compressor and the gas field ion source isprovided. By the cover 417, the influence of vibration caused by thesound of the compressor can be reduced. As a result, high-resolutionobservation is realized. Also in the examples shown in FIGS. 1, 7, and8, a cover may be provided in order to reduce the influence of vibrationcaused by the sound of the compressor.

Although the second helium gas is circulated by using the heliumcompressor 400 in the embodiment, a similar effect is produced by,although not shown, making the pipes 111 and 112 of the heliumcompressor 16 communicated via a flow adjustment valve and making thepipes 409 and 416 communicated via a flow adjustment valve, supplyingcirculation helium gas as a second helium gas, which is a part of thehelium gas of the helium compressor 16 into the pipe 409, and collectingthe gas by the helium compressor 16 via the pipe 416.

Although the GM-type refrigerator 40 is used in the example, in place ofit, a pulse tube refrigerator or Stirling refrigerator may be used.Although the refrigerator has two cooling stages in the example, therefrigerator may have a single cooling stage. The number of coolingstages is not limited. For example, when a helium circulationrefrigerator using small-sized Stirling refrigeration having one coolingstage, and whose lowest cooling temperature is 50K is employed, acompact, low-cost ion beam device can be realized. In this case, neongas or hydrogen may be used in place of the helium gas.

With reference to FIGS. 13A and 13B, a fourth example of the ionmicroscope according to the present invention will be described. Thestructure of an ionization chamber of a gas field ion source will now beexplained. The embodiment is characterized by a wiring structure of theionization chamber. The gas field ion source has a heating power source134 for heating the emitter tip 21, a high-voltage power source 135 forsupplying acceleration voltage to accelerate ions to the emitter tip 21,an extraction power source 141 for supplying extraction voltage toextract the ions to the extraction electrode 24, and a heating powersource 142 for heating the resistive heater 30.

The heating power sources 134 and 143 may be set to 10V, thehigh-voltage power source 135 may be set to 30 kV, and the extractionpower source 141 may be set to 3 kV.

As shown in FIG. 13B, the filament 22 and the high-voltage power source135 are connected via a thick line 133 made of copper and a thin line136 made of a high-temperature superconductor material. The filament 22and the heating power source 134 are connected to each other via thethick line 133 made of copper. The resistive heater 30 and the heatingpower source 142 are connected to each other via a thin line 138 made ofcopper and a thin line 139 made of a high-temperature superconductormaterial. The extraction electrode 24 and the resistive heater 30 havethe same potential.

The thick line 133 made of copper is provided with a cutting mechanism137. The cutting mechanism 137 has a movable mechanism and moves betweentwo positions; a cutting position where the thick line 133 made ofcopper is cut from the filament 22, and a connection position where thethick line 133 made of copper is connected to the filament 22. The thickline 138 made of copper is provided with a cutting mechanism 140. Thecutting mechanism 140 has a movable mechanism and moves between twopositions; a cutting position where the thick line 138 made of copper iscut from the resistive heater 30, and a connection position where thethick line 138 made of copper is connected to the resistive heater 30.FIG. 13A shows a state where both of the cutting mechanisms 137 and 140are in the connection positions, and FIG. 13B shows a state where bothof the cutting mechanisms 137 and 140 are in the cutting positions. Whenthe cutting mechanisms 137 and 140 are in the cutting positions, heatcan be prevented from flowing in the filament 22 and the extractionpower source 141 via the thick lines 133 and 138 made of copper,respectively. The cutting mechanisms 137 and 140 can be operated fromthe outside of the vacuum vessel.

In the example, an on-off valve for opening/closing the ionizationchamber 15 is attached. The on-off valve has a cover member 34. FIG. 13Ashows a state where the cover member 34 is open, and FIG. 13B shows astate where the cover member 34 is closed.

The operation of the gas field ion source of the example will bedescribed. First, as shown in FIG. 13A, coarse exhaust is performed in astate where the cover member 34 of the ionization chamber 15 is open.Since the cover member 34 of the ionization chamber 15 is open, thecoarse exhaust of the ionization chamber 15 completes in short time.

Subsequently, by heating the extraction electrode 24, the side wall 28,and the top plate 29 by the resistive heater 30 on the outside of theside wall of the ionization chamber 15, degasifying process isperformed. After completion of the degasifying process, as shown in FIG.13B, the cutting mechanism 140 is moved to the cutting position. In sucha manner, heat is prevented from flowing in the ionization chamber 15via the thick line 138 made of copper.

The cover member 34 of the ionization chamber 15 is closed and helium issupplied from the gas supply pipe 25. High voltage is supplied to theemitter tip 21 and the extraction voltage is applied to the extractionelectrode 24. When an ion beam is generated from the end of the emittertip 21, the cutting mechanism 137 is moved to the cutting position. Insuch a manner, heat is prevented from flowing in the ionization chamber15 via the thick line 133 made of copper. When the cutting mechanism 137is in the cutting position, the acceleration voltage from thehigh-voltage power source 135 is not applied to the filament 22 via thethick line 133 made of copper but is applied to the filament 22 via thethin line 137 made of high-temperature superconductor material. When thecutting mechanism 140 is in the cutting position, the extraction voltagefrom the extraction power source 141 is not applied to the extractionpower source 141 via the thick line 138 made of copper but is applied tothe filament 22 via the thin line 139 made of high-temperaturesuperconductor material. The filament 22 and the extraction power source141 are always connected to the thin lines 136 and 139 made ofhigh-temperature superconductor material, respectively. Therefore, thereis the possibility that heat flows in the ionization chamber 15 via thethin lines 136 and 138 made of stainless steel. However, the section ofeach of the thin lines 136 and 139 made of stainless steel issufficiently small, so that the amount of heat transmitted via the thinlines 136 and 139 made of high-temperature superconductor material issufficiently small.

With the wiring structure of the example, the heat inflow from thecopper wire to the ionization chamber 15 can be avoided. Consequently,the emitter tip and the extraction electrode can be held at desiredtemperature. That is, improvement in brightness of the ion source andthe higher current of the ion beam can be achieved. Further,high-resolution observation is realized.

Although the thick line made of copper is used in the embodiment, anultrafine wire made of high-temperature superconductor material may beused. In this case, the electric resistance is extremely low atextremely low temperature, so that the ultrafine wire is sufficient topass filament current. An effect is produced such that heat inflow tothe ionization chamber 15 can be avoided also in the case where the wireis not disconnected by the cutting mechanism.

In the example, by providing the ionization chamber 15 with the covermember 34, even when the dimension of the hole in the extractionelectrode is decreased, the conductance at the time of coarse vacuumingcan be increased. By decreasing the dimension of the hole in theextraction electrode, the sealing performance of the ionization chamber15 can be increased. It realizes higher vacuum in the ionization chamber15 and a higher-current ion beam can be obtained.

The wiring structure described above can also be applied to the examplesshown in FIGS. 1, 10, and 12.

The above-described scan ion microscope obtains a scan ion image byperforming scanning with an ion beam by the ion beam scanning electrode.In this case, however, the ion beam tilts when it passes through the ionlens, so that the ion beam is distorted. There is consequently a problemsuch that the beam diameter is large. In place of performing scanningwith the ion beam, the sample stage may be mechanically moved forscanning in two orthogonal directions. In this case, by detectingsecondary particles released from a sample and performing brightnessmodulation on the secondary particles, a scan ion image can be obtainedon image display means of a computer processor. That is, high-resolutionobservation of less than 0.5 nm of a sample surface is realized. In thiscase, an ion beam can be always held in the same direction with respectto the objective lens, so that distortion of the ion beam can be maderelatively small.

It can be realized, for example, by using a sample stage obtained bycombining first and second stages. The first stage is a four-axismovable stage which can move by a few centimeters, and can move, forexample, in two perpendicular directions (X and Y directions) of a planeand a height direction (Z direction) and can move obliquely (Tdirection). The second stage is a biaxial movable stage which can moveby a few micrometers and can move, for example, in two perpendiculardirections (X and Y directions) of a plane.

For example, the sample stage is constructed by disposing the secondstage driven by a piezo element on the first stage driven by an electricmotor. In the case of retrieving a sample observation position or thelike, the sample is moved by using the first stage. In the case ofhigh-resolution observation, the sample is finely moved by using thesecond stage. With the configuration, the ion microscope capable ofperforming ultrahigh resolution observation is provided.

The scan ion microscope has been described above as an example of theion beam device of the present invention. However, the ion beam deviceof the invention is not limited to the scan ion microscope but can alsobe applied to a transmission ion microscope and an ion beam machiningdevice.

Next, the vacuum pump 12 for evacuating the gas field ion source will bedescribed. Preferably, the vacuum pump 12 is constructed by acombination of a non-evaporable Getter pump and an ion pump, acombination of a non-evaporable Getter pump and a noble pump, or acombination of a non-evaporable Getter pump and an excel pump. Asublimation pump may also be employed. It has been found that, by usingany of such pumps, the influence of vibration of the vacuum pump 12 canbe reduced, and high-resolution observation is realized. It has beenfound that, in the case of using a turbo molecule pump as the vacuumpump 12, the vibration of the turbo molecule pump sometimes disturbsobservation of a sample with an ion beam. It has also been found thateven when a turbo molecule pump is attached to the vacuum vessel of anyof the ion beam devices, by stopping the turbo molecule pump at the timeof observing a sample with an ion beam, high-resolution observation ispossible. That is, in the present invention, although a main evacuationpump at the time of observation of a sample with an ion beam isconstructed by a combination of a non-evaporable Getter pump and an ionpump, a combination of a non-evaporable Getter pump and a noble pump, ora combination of a non-evaporable Getter pump and an excel pump. Even ifa turbo molecule pump is attached, the object of the present inventionis not disturbed.

The non-evaporable Getter pump is a vacuum pump made of an alloy whichadsorbs gas when activated by heating. In the case of using helium asthe ionization gas of the gas field ion source, a relatively largeamount of helium exists in the vacuum vessel. However, thenon-evaporable Getter pump hardly exhausts helium. That is, the Gettersurface is not saturated by absorption gas molecules. Consequently, theoperation time of the non-evaporable Getter pump is sufficiently long.This is an advantage in the case of combining the helium ion microscopeand the non-evaporable Getter pump. An effect such that since theimpurity gas in the vacuum vessel decreases, the ion release currentbecomes stable is also produced.

Although the non-evaporable Getter pump exhausts residual gas except forhelium at high exhaust speed, helium remains in the ion source only bythe exhaust. Due to this, the degree of vacuum becomes insufficient, andthe gas field ion source does not operate normally. To address it, anion pump or noble pump having high speed of exhaust of inactive gas isused in combination with the non-evaporable Getter pump. When only anion pump or noble pump is used, exhaust speed is insufficient. Accordingto the present invention, by combining the non-evaporable Getter pumpand the ion pump or noble pump, the compact, low-cost vacuum pump 12 canbe obtained. As the vacuum pump 12, a pump obtained by combining aGetter pump or a titanium sublimation pump which evaporates metal suchas titanium by heating, adsorbs gas molecules by a metal film, andevacuates may also be used.

Although the sufficient performance of the ion microscope is notobtained due to insufficient consideration on the mechanical vibrationin the conventional techniques, the present invention realizes reductionin the mechanical vibration and provides the gas field ion source andthe ion microscope by which high-resolution observation can beperformed.

Next, the sample chamber evacuation pump 13 for evacuating the samplechamber 3 will be described. As the sample chamber evacuation pump 13, aGetter pump, a titanium sublimation pump, a non-evaporable Getter pump,an ion pump, a noble pump, an excel pump, or the like may be used. Ithas been found that, by using any of such pumps, the influence ofvibration of the sample chamber evacuation pump 13 can be reduced, andhigh-resolution observation is realized.

A turbo molecule pump may be used as the sample chamber evacuation pump13. However, it costs to realize a structure of lessening vibration of adevice. It has been found that even when a turbo molecule pump isattached in a sample chamber, by stopping the turbo molecule pump at thetime of observing a sample with an ion beam, high-resolution observationcan be made. In the present invention, a main evacuation pump in thesample chamber at the time of observation of a sample with an ion beamis constructed by a combination of a non-evaporable Getter pump and anion pump, a combination of a non-evaporable Getter pump and a noblepump, or a combination of a non-evaporable Getter pump and an excelpump. Even if a turbo molecule pump is attached as a device componentand used for coarse vacuuming from atmosphere, the object of the presentinvention is not disturbed.

The scanning electron microscope can realize resolution of 0.5 nm orless by using the turbo molecule pump relatively easily. However, in anion microscope using a gas field ion source, the reduction ratio of anion beam from the ion light source to a sample is relatively large andis about 1 to 0.5. Consequently, the characteristic of the ion sourcecan be utilized maximally. However, the vibration of the ion emitter isreproduced on a sample without being hardly reduced, so that a carefulmeasure which is more than a vibration measure in a conventionalscanning electron microscope or the like is necessary.

In the conventional techniques, the fact that the vibration of thesample chamber evacuation pump exerts an influence on the sample stageis considered, but the fact that the vibration of the sample chamberevacuation pump exerts an influence even on the ion emitter is notconsidered. The inventors of the present invention therefore have foundout that the vibration of the sample chamber evacuation pump exerts aserious influence on the ion emitter. The inventors of the presentinvention have thought that it is preferable to use, as the samplechamber evacuation pump, a non-vibration-type vacuum pump as a main pumpsuch as a Getter pump, a titanium sublimation pump, a non-evaporableGetter pump, an ion pump, a noble pump, or an excel pump. With the mainpump, the vibration of the ion emitter is reduced, and high-resolutionobservation is realized.

There is the possibility that the compressor unit (compressor) for thegas of the refrigerator or the compressor unit (compressor) for makinghelium circulate used in the example becomes the source of noise. Thenoise sometimes makes the ion microscope vibrate. Consequently,according to the present invention, by providing the gas compressor unit(compressor) with a cover as in the example shown in FIG. 9, noise whichis generated by the gas compressor unit is prevented from beingtransmitted to the outside. In place of the cover, a sound shield platemay be provided. The compressor unit (compressor) may be mounted inanother room. With the configuration, vibration caused by sound isreduced, and high-resolution observation is realized.

A non-evaporable Getter material may be disposed in the ionizationchamber. With the configuration, the inside of the ionization chamber isin high vacuum and very-stable ion emission is realized. Alternately,the non-evaporable Getter material or hydrogen storing alloy is allowedto adsorb hydrogen and is heated. By using hydrogen released by theheating as ionization gas, it becomes unnecessary to supply gas from thegas supply pipe 25. A compact and safe gas supply mechanism can berealized.

A non-evaporable Getter material may be disposed in the gas supply pipe25. Impurity gas in the gas supplied via the gas supply pipe 25 isreduced by the non-evaporable Getter material. Consequently, ionemission current becomes stable.

In the invention, helium or hydrogen is used as the ionization gassupplied to the ionization chamber 15 via the gas supply pipe 25. As theionization gas, neon, oxygen, argon, krypton, xenon, or the like mayalso be used. In particular, in the case o suing neon, oxygen, argon,krypton, xenon, or the like, an effect such that a sample processingdevice or a sample analyzing device is provided is produced.

A mass spectrometer may be provided in the sample chamber 3. The massspectrometer conducts mass analysis on secondary ions emitted from asample or energy analysis on Auger electrons emitted from a sample. Theanalysis facilitates sample element analysis, and sample observation andthe element analysis by the ion microscope can be performed by a singledevice.

In the ion microscope of the present invention, by applying highnegative voltage to the emitter tip, electrons can also be extractedfrom the emitter tip. A sample is irradiated with an electron beam andan X-ray or Auger electron emitted from the sample is detected. Thedetection facilitates sample element analysis, and sample observationand the element analysis of high resolution by the ion microscope can beperformed by a single device.

In this case, an ion image having a resolution of 1 nm or less and anelement analysis image may be displayed side by side or overlappingly.By the display, the sample surface can be preferably subjected tocharacterization.

When a composite lens obtained by combining a magnetic-field lens and anelectrostatic lens is used as the objective lens for focusing anelectron beam, an electron beam can be focused to a high-current beamhaving a very small diameter, so that an element analysis ofhigh-spatial resolution and high sensitivity is realized.

Although disturbance of an external magnetic field is not considered inthe conventional ion beam device, the inventors of the present inventionhave found that, in the case of focusing an ion beam to a value which isless than 0.5 nm, it is effective to shield the magnetic field.Consequently, by forming the gas field ion source, the ion beamirradiation system, and the vacuum chamber in the sample chamber of pureiron or permalloy, ultrahigh resolution can be achieved. A plate as amagnetic shield may be inserted in the vacuum vessel.

The inventors of the present invention have found that when the ion beamacceleration voltage is set to 50 kV or higher, the structure dimensionsof a semiconductor sample can be measured with high precision. Since thesputter yield of a sample with an ion beam decreases, the degree ofdestroying the structure of the sample becomes low, and the dimensionalmeasurement precision improves. In particular, when hydrogen is used asionization gas, the sputter yield decreases, and the precision of thedimensional measurement improves.

As described above, the present invention provides an analyzer suitablefor measuring structural dimensions of a sample with an ion beam and alength measuring device or an inspection device using an ion beam.

Since the depth of focus of an image obtained in the present inventionis deeper than that in measurement with a conventional electron beam,measurement with higher precision can be performed. Particularly, whenhydrogen is used as the ionization gas, the amount of etching the samplesurface is smaller and measurement with higher precision can beperformed.

The present invention provides a length measuring device or aninspection device using an ion beam suitable to measure structuraldimensions of a sample.

In place of a device of forming a section by processing a sample with anion beam and observing the section by an electron microscope, theinvention can provide a device of forming a section by processing asample with an ion beam and observing the section by an ion microscopeand a section observing method.

The invention can provide a device capable of performing sampleobservation by an ion microscope, sample observation by an electronmicroscope, and an element analysis by a single device, an analyzingdevice for observing and analyzing a defect, a foreign matter, or thelike, and an inspection device.

The ion microscope realizes ultrahigh resolution. However,conventionally, the influence on manufacture of destruction of a surfaceof a semiconductor sample of ion beam irradiation in the case of usingan ion beam device as a device of measuring structural dimensions in aprocess of manufacturing a semiconductor sample or an inspection deviceis not considered in comparison with the case of electron beamirradiation. For example, when the energy of an ion beam is set to lessthan 1 keV, the ratio that a sample becomes modified is low and, incomparison with the case where energy of an ion beam is set to 20 keV,the precision of dimensional measurement improves. In this case, aneffect such that the cost of the device becomes also lower is produced.On the contrary, in the case where acceleration voltage is 50 kV orhigher, the observation resolution can be made higher than that in thecase where the acceleration voltage is low.

The inventors of the present invention found that by setting the ionbeam acceleration voltage to 200 kV or higher, decreasing the beamdiameter to 0.2 nm or less, irradiating a sample with the resultant ionbeam, and energy-analyzing ions which are Rutherford-back-scattered fromthe sample, a three-dimensional structure including a plane of a sampleelement and depth can be measured in atomic unit. In a conventionalRutherford back scattering device, the ion beam diameter is large, andit is difficult to perform three-dimensional measurement in the atomicorder. However, by applying the present invention, the three-dimensionalmeasurement in the atomic order can be realized. By setting the ion beamacceleration voltage to 500 kV or higher, decreasing the beam diameterto 0.2 nm or less, irradiating a sample with the ion beam, andenergy-analyzing an X ray released from the sample, two-dimensionalanalysis of a sample element can be performed.

The present invention discloses the following gas field ion source, anion microscope, and an ion beam device.

-   -   (1) A gas field ion source including a vacuum vessel, an        evacuation mechanism, an emitter tip as a needle-shaped anode,        and an extraction electrode as a cathode, supplying a gas        molecule close to the end of the emitter tip, and ionizing the        gas molecule at the end of the emitter tip with an electric        field, wherein a mount of the emitter tip and the extraction        electrode are connected by including a shape-changeable        mechanism part, and an ionization chamber in which the emitter        tip is almost surrounded by at least the mount of the emitter        tip, the extraction electrode, and the shape-changeable        mechanism part is deformable in the vacuum vessel without hardly        in contact with the vacuum vessel.    -   (2) The gas field ion source of (1), wherein when the gas        molecule is supplied in the ionization chamber, gas pressure in        the ionization chamber can be made higher than that in the        vacuum chamber by at least one digit.    -   (3) The gas field ion source of (1), wherein the mount of the        emitter tip is connected to the vacuum vessel while including        another shape-changeable mechanism part.    -   (4) The gas field ion source of any of (1) to (3), wherein the        shape-changeable mechanism part is a bellows.    -   (5) The gas field ion source according to (4), wherein the        smallest diameter of the bellows existing between the emitter        tip mount and the extraction element is smaller than the maximum        diameter of the bellows existing between the emitter tip mount        and the vacuum vessel.    -   (6) An ion beam device including: an ion beam device body        including a gas field ion source having a vacuum vessel, an        evacuation mechanism, in the vacuum vessel, an emitter tip as a        needle-shaped anode, an extraction electrode as a cathode, a        mechanism for cooling the emitter tip, and the like, supplying a        gas molecule close to the end of the emitter tip, and ionizing        the gas molecule at the end of the emitter tip with an electric        field, a lens system for focusing an ion beam extracted from the        emitter tip, a sample chamber including a sample, and a        secondary particle detector for detecting secondary particles        emitted from the sample; a base plate on which the ion beam        device body is mounted; and a stand for supporting the base        plate, wherein a vibration preventing mechanism is provided        between the ion beam device body and the base plate, the cooling        mechanism is supported by a floor on which the ion beam device        is mounted or a supporting mechanism fixed to the ion beam        device base and, further, a vibration preventing mechanism is        provided between the refrigerator and the vacuum vessel.    -   (7) The ion beam device of (6), wherein the cooling mechanism        has cold generating means which generates cold by making        high-pressure gas generated by the compressor unit expand, and a        refrigerator for cooling the stage by the cold of the cold        generating means.    -   (8) The ion beam device of (6), wherein the cooling mechanism        has cold generating means which generates cold by making first        high-pressure gas generated by the compressor unit expand, and        cooling means for cooling a member to be cooled by the gas        cooled by the cold of the cold generating means.    -   (9) The ion beam device of (6), wherein the cooling mechanism        has cold generating means which generates cold by making first        high-pressure gas generated by the compressor unit expand, and        cooling means for cooling a member to be cooled by a second        high-pressure gas which is cooled by the cold of the cold        generating means.    -   (10) The ion beam device of (6), wherein the vibration        preventing mechanism existing between the refrigerator and the        vacuum vessel includes at least a mechanism of disturbing        transmission of vibration by helium or neon gas.    -   (11) The ion beam device of (6), wherein at least a        shape-changeable mechanism part exists between the cooling stage        of the cooling mechanism and an emitter tip.    -   (12) The ion beam device of (6), wherein the cooling mechanism        is a mechanism of holding a refrigerant obtained by setting a        refrigerant gas which is in a gas state at normal temperature in        atmosphere into a liquid or solid state in a vacuum vessel, the        vacuum vessel is connected while sandwiching at least one        vibration preventing mechanism part to a vacuum vessel of the        ion beam device, and a place cooled by the refrigerant and the        emitter tip are connected while sandwiching at least one        shape-changeable mechanism part.    -   (13) The gas field ion source of (12), wherein a mechanism of        varying conductance to evacuate the ion chamber is a valve which        can be operated from the outside of the vacuum vessel, and can        be mechanically detached from a wall structure of the ionization        chamber.    -   (14) The gas field ion source of (1), further including a        resistive heater capable of heating the ionization chamber,        wherein the resistive heater can be mechanically disconnected by        operating at least one of a plurality of electric wires        connected to the resistive heater from the outside of vacuum.    -   (15) The gas field ion source of (1), wherein the refrigerant of        the cooling mechanism is a refrigerant obtained by setting a        refrigerant gas which is in a gas state at normal temperature in        atmosphere into a solid state.    -   (16) An ion microscope including the gas field ion source of any        of (1) to (5) or (13) to (15), a lens system for focusing an ion        extracted from the gas field ion source, a secondary particle        detector for detecting a secondary particle, and an image        display unit for displaying an ion microscope image.

The present invention discloses the following ion microscope, an ionbeam device, and an ion beam inspection device.

-   -   (17) An ion beam device including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, and an extraction        electrode as a cathode, a mechanism for cooling the emitter tip,        and the like, supplying a gas molecule close to the end of the        emitter tip, and ionizing the gas molecule at the end of the        emitter tip with an electric field; a lens and an objective lens        for focusing an ion beam extracted from the emitter tip; a        sample chamber housing a sample; and a secondary particle        detector for detecting a secondary particle released from the        sample, wherein distance from the end of the objective lens to        the surface of the sample is made short to a value less than 2        mm, and the ion beam diameter is reduced to a value less than        0.2 nm.    -   (18) An ion microscope including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, and an extraction        electrode as a cathode, a mechanism for cooling the emitter tip,        and the like, supplying a gas molecule close to the end of the        emitter tip, and ionizing the gas molecule at the end of the        emitter tip with an electric field; a lens system for focusing        an ion beam extracted from the emitter tip; a sample chamber        housing a sample; and a secondary particle detector for        detecting a secondary particle released from the sample, wherein        the sample chamber can be heated to about 200° C. to increase        the degree of vacuum in the sample chamber to 10⁻⁷ Pa at the        maximum.    -   (19) An ion microscope including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, and an extraction        electrode as a cathode, a mechanism for cooling the emitter tip,        and the like, supplying a gas molecule close to the end of the        emitter tip, and ionizing the gas molecule at the end of the        emitter tip with an electric field; a lens system for focusing        an ion beam extracted from the emitter tip; a sample chamber        housing a sample; a secondary particle detector for detecting a        secondary particle released from the sample; and a vacuum pump        for evacuating the sample chamber, wherein a main vacuum pump        for evacuating the sample chamber during observation by the ion        microscope includes any of a sublimation pump, a non-evaporable        Getter pump, an ion pump, a noble pump, and an excel pump.    -   (20) An ion microscope including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, and an extraction        electrode as a cathode, a mechanism for cooling the emitter tip,        and the like, supplying a gas molecule close to the end of the        emitter tip, and ionizing the gas molecule at the end of the        emitter tip with an electric field; a vacuum pump for evacuating        the gas field ion source; a lens system for focusing an ion beam        extracted from the emitter tip; a sample chamber housing a        sample; and a secondary particle detector for detecting a        secondary particle released from the sample, wherein a main        vacuum pump for evacuating the gas field ion source during        observation by the ion microscope includes any of a sublimation        pump, a non-evaporable Getter pump, an ion pump, a noble pump,        and an excel pump.    -   (21) An ion microscope including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, an extraction electrode        as a cathode, a vessel of a liquid cryogen for a mechanism for        cooling the emitter tip, a vacuum pump for evacuating the vessel        of the liquid cryogen, and the like, supplying a gas molecule        close to the end of the emitter tip, and ionizing the gas        molecule at the end of the emitter tip with an electric field; a        vacuum pump for evacuating the gas field ion source; a lens        system for focusing an ion beam extracted from the emitter tip;        a sample chamber housing a sample; and a secondary particle        detector for detecting a secondary particle released from the        sample, wherein a controller for controlling temperature of the        vessel of the liquid cryogen by controlling operation of the        vacuum pump by measurement of the degree of vacuum in the vessel        of the liquid cryogen or temperature measurement is provided.    -   (22) An ion beam device including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, an extraction electrode        as a cathode, a vessel of a liquid cryogen for a mechanism for        cooling the emitter tip, a vacuum pump for evacuating the vessel        of the liquid cryogen, and the like, supplying a gas molecule        close to the end of the emitter tip, and ionizing the gas        molecule at the end of the emitter tip with an electric field; a        lens system for focusing an ion beam extracted from the emitter        tip; a sample chamber housing a sample; and a secondary particle        detector for detecting a secondary particle released from the        sample, wherein the cooling mechanism is a refrigerator for        cooling a stage of the refrigerator by cold of cold generating        means which generates cold by making high-pressure gas generated        by a compressor unit expand, and sound from the compressor unit        of the gas is reduced by providing the compressor unit for        generating the high-pressure gas with a cover.    -   (23) An ion beam device including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, an extraction electrode        as a cathode, a vessel of a liquid cryogen for a mechanism for        cooling the emitter tip, a vacuum pump for evacuating the vessel        of the liquid cryogen, and the like, supplying a gas molecule        close to the end of the emitter tip, and ionizing the gas        molecule at the end of the emitter tip with an electric field; a        lens system for focusing an ion beam extracted from the emitter        tip; a sample stage having at least two kinds of moving        mechanisms in at least two directions in a plane irradiated with        an ion beam; a sample chamber housing a sample mounted on the        sample stage; and a secondary particle detector for detecting a        secondary particle released from the sample, wherein the sample        stage is mechanically moved in two orthogonal directions,        detecting secondary particles released from the sample, and        obtaining an ion microscope image.    -   (24) The ion beam device of (23), wherein the sample stage        having at least two kinds of moving mechanisms in at least two        directions in a plane irradiated with the ion beam includes at        least a stage using a piezo element driving mechanism, and        resolution of an ion microscope image is less than 0.5 nm.    -   (25) An ion beam device including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, and an extraction        electrode as a cathode, a mechanism for cooling the emitter tip,        a gas supply pipe, and the like, supplying a gas molecule close        to the end of the emitter tip, and ionizing the gas molecule at        the end of the emitter tip with an electric field; a lens system        for focusing an ion beam extracted from the emitter tip; a        sample chamber housing a sample; a secondary particle detector        for detecting a secondary particle released from the sample; and        a vacuum pump for evacuating the sample chamber; and a vacuum        pump for evacuating the sample chamber, wherein a non-evaporable        Getter material is mounted in a supply pipe by using an inactive        gas of helium, neon, argon, krypton, xenon, or the like.    -   (26) An ion beam device including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, and an extraction        electrode as a cathode, a mechanism for cooling the emitter tip,        and the like, supplying a gas molecule close to the end of the        emitter tip, and ionizing the gas molecule at the end of the        emitter tip with an electric field; a vacuum pump for evacuating        the gas field ion source; a lens and an objective lens for        focusing an ion beam extracted from the emitter tip; a sample        chamber housing a sample; and a secondary particle detector for        detecting a secondary particle released from the sample, wherein        by applying high negative voltage to the emitter tip, extracting        electrons from the emitter tip, irradiating a sample with the        electrons, and detecting an X-ray or Auger electron emitted from        the sample, an element analysis can be performed, and a scanning        ion image having a resolution of 1 nm or less and an element        analysis image are displayed side by side or overlappingly.    -   (27) An ion beam inspection device including: a gas field ion        source having a vacuum vessel, an evacuation mechanism, in the        vacuum vessel, an emitter tip as a needle-shaped anode, and an        extraction electrode as a cathode, a mechanism for cooling the        emitter tip, and the like, supplying a gas molecule close to the        end of the emitter tip, and ionizing the gas molecule at the end        of the emitter tip with an electric field; a vacuum pump for        evacuating the gas field ion source; a lens and an objective        lens for focusing an ion beam extracted from the emitter tip;        and a sample chamber housing a sample, for detecting a secondary        particle released from the sample and measuring a structural        dimension of a sample surface, wherein voltage for acceleration        an ion beam is set to 50 kV or higher, and a structural        dimension on a semiconductor sample is measured.    -   (28) The ion beam inspection device according to (27), wherein        hydrogen gas is used.    -   (29) An ion beam inspection device including: a gas field ion        source having a vacuum vessel, an evacuation mechanism, in the        vacuum vessel, an emitter tip as a needle-shaped anode, and an        extraction electrode as a cathode, a mechanism for cooling the        emitter tip, and the like, supplying a gas molecule close to the        end of the emitter tip, and ionizing the gas molecule at the end        of the emitter tip with an electric field; a vacuum pump for        evacuating the gas field ion source; a lens and an objective        lens for focusing an ion beam extracted from the emitter tip;        and a sample chamber housing a sample, for detecting a secondary        particle released from the sample and measuring a structural        dimension of a sample surface, wherein energy of an ion beam is        set to be less than 1 keV.    -   (30) An ion beam device including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, an extraction electrode        as a cathode, a mechanism for cooling the emitter tip, and the        like, supplying a gas molecule close to the end of the emitter        tip, and ionizing the gas molecule at the end of the emitter tip        with an electric field; a vacuum pump for evacuating the gas        field ion source; a lens and an objective lens for focusing an        ion beam extracted from the emitter tip; a sample chamber        housing a sample; and a secondary particle detector for        detecting a secondary particle released from the sample, wherein        a negative high voltage is applied to the emitter tip to extract        electrons from the emitter tip, the electrons are allowed to        pass through a composite-type objective lens obtained by        combining a magnetic field lens and an electrostatic lens and        are emitted to the sample, an X-ray or Auger electron released        from the sample is detected, and element analysis can be        performed.    -   (31) An element analyzing method using an ion beam device        including: a gas field ion source having a vacuum vessel, an        evacuation mechanism, in the vacuum vessel, an emitter tip as a        needle-shaped anode, and an extraction electrode as a cathode, a        mechanism for cooling the emitter tip, and the like, supplying a        gas molecule close to the end of the emitter tip, and ionizing        the gas molecule at the end of the emitter tip with an electric        field; a lens and an objective lens for focusing an ion beam        extracted from the emitter tip; a sample chamber housing a        sample; and a secondary particle detector for detecting a        secondary particle released from the sample, wherein        acceleration voltage for an ion beam is set to 200 kV or higher,        a beam diameter is reduced to 0.2 nm or less, a sample is        irradiated with the resultant ion beam, ions which are        Rutherford-backscattered from the sample are energy-analyzed,        and a three-dimensional structure including a plane and depth of        a sample element is measured in atomic unit.    -   (32) A sample element analyzing method using an ion beam device        including: a gas field ion source having a vacuum vessel, an        evacuation mechanism, in the vacuum vessel, an emitter tip as a        needle-shaped anode, and an extraction electrode as a cathode, a        mechanism for cooling the emitter tip, and the like, supplying a        gas molecule close to the end of the emitter tip, and ionizing        the gas molecule at the end of the emitter tip with an electric        field; a lens and an objective lens for focusing an ion beam        extracted from the emitter tip; a sample chamber housing a        sample; and a secondary particle detector for detecting a        secondary particle released from the sample, wherein 500 kV or        higher is set, a beam diameter is reduced to 0.2 nm or less, a        sample is irradiated with the resultant ion beam, an X-ray        released from the sample is energy-analyzed, and a        two-dimensional element analysis is performed.    -   (33) An ion beam device including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, and an extraction        electrode as a cathode, a mechanism for cooling the emitter tip,        and the like, supplying a gas molecule close to the end of the        emitter tip, and ionizing the gas molecule at the end of the        emitter tip with an electric field; a lens and an objective lens        for focusing an ion beam extracted from the emitter tip; a        sample chamber housing a sample; and a secondary particle        detector for detecting a secondary particle released from the        sample, wherein the emitter tip is cooled to 50K or less, a        magnification of projecting an ion released from the emitter tip        onto a sample is set to be less than 0.2, and vibration of a        relative position between the emitter tip and the sample is set        to 0.1 nm or less, thereby setting resolution of a scanning ion        image to be 0.2 nm or less.    -   (34) An ion beam device including: a gas field ion source having        a vacuum vessel, an evacuation mechanism, in the vacuum vessel,        an emitter tip as a needle-shaped anode, and an extraction        electrode as a cathode, a mechanism for cooling the emitter tip,        and the like, supplying a gas molecule close to the end of the        emitter tip, and ionizing the gas molecule at the end of the        emitter tip with an electric field; a lens and an objective lens        for focusing an ion beam extracted from the emitter tip; a        sample chamber housing a sample; and a secondary particle        detector for detecting a secondary particle released from the        sample, wherein a sample stage is of a side entry type, and has        a structure whose end is in contact with a wall face of the        sample chamber.    -   (35) An ion beam device including: a gas field ion source for        generating an ion beam; an ion irradiation system for guiding        the ion beam from the gas field ion source onto a sample; a        vacuum vessel housing the gas field ion source and the ion        irradiation system; a sample chamber housing a sample stage for        holding a sample; and a cooling mechanism of a gas circulation        type for cooling the gas field ion source, wherein the cooling        mechanism has a refrigerator, a pipe connecting the refrigerator        and the gas field ion source, a heat exchanger provided for the        pipe, and a circulation compressor for circulating liquid helium        in the pipe, and the pipe is fixedly supported by a floor or a        supporting member.    -   (36) An ion beam device including: a gas field ion source for        generating an ion beam; an ion irradiation system for guiding        the ion beam from the gas field ion source onto a sample; a        vacuum vessel housing the gas field ion source and the ion        irradiation system; a sample chamber housing a sample stage for        holding a sample; and a cooling mechanism for cooling the gas        field ion source, wherein the cooling mechanism has cold        generating means which generates cold by making first        high-pressure gas generated by a compressor unit expand, and a        cooling mechanism for cooling a member to be cooled by helium        gas as a second movable refrigerant which is circulated by the        compressor unit.    -   (37) An ion beam device including: a gas field ion source for        generating an ion beam; an ion irradiation system for guiding        the ion beam from the gas field ion source onto a sample; a        vacuum vessel housing the gas field ion source and the ion        irradiation system; a sample chamber housing a sample stage for        holding a sample; a cooling mechanism for cooling the gas field        ion source; and a base plate for supporting the field ion        source, the vacuum vessel, and the sample chamber, wherein an        ion beam irradiation path is provided with a magnetic shield        mechanism.    -   (38) An ion beam device including: a gas field ion source for        generating an ion beam; an ion irradiation system for guiding        the ion beam from the gas field ion source onto a sample; a        vacuum vessel housing the gas field ion source and the ion        irradiation system; a sample chamber housing a sample stage for        holding a sample; a cooling mechanism for cooling the gas field        ion source; and a base plate for supporting the gas field ion        source, the vacuum vessel, and the sample chamber, wherein a        main material of a vacuum chamber of any of the gas field ion        source, the ion beam irradiation system, and the sample chamber        is iron or permalloy, and resolution of a scanning ion image is        0.5 nm or less.        Description of Reference Numerals

-   1 . . . gas field ion source

-   2 . . . ion beam irradiation system column

-   3 . . . sample chamber

-   4 . . . cooling mechanism

-   5 . . . condenser lens

-   6 . . . beam limiting aperture

-   7 . . . beam scanning electrode

-   8 . . . objective lens

-   9 . . . sample

-   10 . . . sample stage

-   11 . . . secondary particle detector

-   12 . . . ion source evacuation pump

-   13 . . . sample chamber evacuation pump

-   14 . . . ion beam

-   14A . . . optical axis

-   15 . . . ionization chamber

-   16 . . . compressor

-   17 . . . device stand

-   18 . . . base plate

-   19 . . . vibration preventing mechanism

-   20 . . . floor

-   21 . . . emitter tip

-   22 . . . filament

-   23 . . . filament mount

-   24 . . . extraction electrode

-   25 . . . gas supply pipe

-   26 . . . supporting rod

-   27 . . . hole

-   28 . . . side wall

-   29 . . . top plate

-   30 . . . resistive heater

-   31 . . . opening

-   32 . . . cover member

-   33 . . . operation rod

-   34 . . . cover member

-   40 . . . refrigerator

-   40A . . . center axial line

-   41 . . . main body

-   42A, 42B . . . stages

-   43 . . . pot

-   46 . . . helium gas

-   51 . . . upper flange

-   52 . . . sapphire base

-   53 . . . cooling conduction rod

-   54 . . . copper stranded wire

-   55 . . . sapphire base

-   56 . . . copper stranded wire

-   57 . . . cooling conduction pipe

-   58 . . . radiation shield

-   59 . . . electrostatic lens

-   60 . . . electrode

-   61, 62 . . . bellows

-   63 . . . insulating material

-   64 . . . emitter base mount

-   68 . . . vacuum vessel

-   69 . . . bellows

-   70 . . . vibration preventing mechanism

-   71 . . . diamagnetic block 71

-   72 . . . ring-shaped electromagnet

-   73 . . . supporting member 73

-   74 . . . knob

-   75 . . . superconductor block

-   81 . . . liquid or solid nitrogen chamber

-   82 . . . liquid or solid nitrogen tank

-   83 . . . evacuation port

-   84 . . . solid nitrogen

-   85 . . . supporting pillar

-   86 . . . bellows

-   87 . . . supporting pillar

-   91 . . . field ion source controller

-   92 . . . refrigerator controller

-   93 . . . lens controller

-   94 . . . beam limiting aperture controller

-   95 . . . ion beam scanning controller

-   96 . . . secondary particle detector controller

-   97 . . . sample stage controller

-   98 . . . evacuation pump controller

-   99 . . . computer processor

-   101 . . . surface plate

-   102 . . . vibration preventing leg

-   103, 104 . . . supporting pillar

-   133 . . . electric line

-   134 . . . power source

-   135 . . . high-voltage power source

-   136 . . . thin line made of stainless steel

-   137 . . . cutting mechanism

-   138 . . . thick line made of copper

-   139 . . . thin line made of stainless steel

-   140 . . . cutting mechanism

-   141 . . . ion extraction electrode

-   142 . . . power source

-   301 . . . scanning deflection electrode

-   302 . . . aperture grill

-   303 . . . movable radiation pattern observation mechanism

-   304 . . . secondary particle

-   305 . . . secondary particle detector

1. An ion beam device comprising: a gas field ion source for generatingan ion beam; an objective lens for focusing an ion beam extracted fromthe gas field ion source on a sample; a movable beam limiting aperturewhich limits an open angle of the ion beam to the objective lens; asample stage on which the sample is mounted; and a vacuum vessel whichhouses the gas field ion source, the objective lens, the beam limitingaperture, the sample stage, and the like, wherein the gas field ionsource includes an emitter tip for generating an ion, an emitter basemount which supports the emitter tip, an ionization chamber having anextraction electrode provided so as to be opposed to the emitter tip andconstructed so as to surround the emitter tip, and a gas supply pipe forsupplying gas to vicinity of the emitter tip, and a mechanism whichproduces a noncontact interaction between the emitter base mount and thevacuum vessel is provided so as to suppress fluctuations in positionalrelation of the emitter base mount with respect to the vacuum vessel. 2.The ion beam device according to claim 1, wherein the noncontactinteraction is produced in an ion beam extraction direction or adirection almost perpendicular to the ion beam extraction direction. 3.The ion beam device according to claim 1, wherein the noncontactinteraction is a magnetic interaction which occurs between the emitterbase mount and the vacuum vessel.
 4. The ion beam device according toclaim 3, wherein at least a part of the emitter base mount is made of adiamagnetic material.
 5. The ion beam device according to claim 3,wherein the magnetic interaction is generated by an electromagnet madeof a superconducting material.
 6. The ion beam device according to claim1, wherein at least a part of the emitter base mount is made of asuperconducting material.
 7. The ion beam device according to claim 6,wherein before extraction of the ion beam, by cooling a part of theemitter base mount, the part enters a superconducting state.
 8. The ionbeam device according to claim 6, wherein a permanent magnet fixed tothe vacuum vessel is disposed around the emitter base mount.
 9. The ionbeam device according to claim 3, wherein a permanent magnet is disposedat least in a part of the emitter base mount, and a bulk superconductorfixed to the vacuum vessel is disposed around the emitter base mount.10. The ion beam device according to claim 3, wherein a permanent magnetis disposed on the emitter base mount, and a bulk superconductor isdisposed on a side wall of the ionization chamber.
 11. The ion beamdevice according to claim 3, wherein a bulk superconductor is disposedon the emitter base mount, and a permanent magnet is disposed on a sidewall of the ionization chamber.
 12. The ion beam device according toclaim 6, wherein a position of the emitter base mount is controlled by amagnetic field intensity distribution control mechanism disposed in theperiphery of the emitter base mount.
 13. The ion beam device accordingto claim 12, wherein the magnetic field intensity distribution controlmechanism is a mechanism of controlling magnetic field intensities of aplurality of electromagnets disposed around the emitter base mount. 14.The ion beam device according to claim 1, wherein the gas field ionsource further includes a filament connected to the emitter tip, a powersource for supplying voltage to the filament, and a wire connecting thefilament and the power source, and at least a part of a wire in the gasfield ion source is made of a superconductor material.
 15. The ion beamdevice according to claim 1, wherein the gas field ion source includes aheater for heating the ionization chamber, a heater power source forsupplying power to the heater, and a wire connecting the heater and theheater power source, and at least a part of the wire in the gas fieldion source is made of a superconducting material.
 16. An ion beam devicecomprising: a gas field ion source for generating an ion beam; anobjective lens for focusing an ion beam from the gas field ion source ona sample; a movable beam limiting aperture which limits an open angle ofthe ion beam to the objective lens; a sample stage on which the sampleis mounted; and a vacuum vessel which houses the gas field ion source,the objective lens, the beam limiting aperture, the sample stage, andthe like, wherein the gas field ion source includes an emitter tip forgenerating an ion, an emitter base mount which supports the emitter tip,an ionization chamber having an extraction electrode provided so as tobe opposed to the emitter tip and constructed so as to surround theemitter tip, and a gas supply pipe for supplying gas to vicinity of theemitter tip, and when the beam limiting aperture is a hole opened in aplate, a predetermined tilt angle is formed by an irradiation directionof the ion beam and a normal to the plate.
 17. The ion beam deviceaccording to claim 16, wherein an angle formed by the irradiationdirection of the ion beam and the normal to the plate is at least 45degrees or higher.
 18. The ion beam device according to claim 17,wherein gas molecules of at least two kinds of mass numbers can beemitted, the gas molecule of the larger mass number is emitted, afterthat, the gas molecule of the smaller mass number is irradiated, and asample is observed.
 19. An ion beam device comprising: a gas field ionsource for generating an ion beam; an objective lens for focusing an ionbeam from the gas field ion source on a sample; a movable beam limitingaperture which limits an open angle of the ion beam to the objectivelens; a sample stage on which the sample is mounted; and a vacuum vesselwhich houses the gas field ion source, the objective lens, the beamlimiting aperture, the sample stage, and the like, wherein the gas fieldion source includes an emitter tip for generating an ion, an emitterbase mount which supports the emitter tip, an ionization chamber havingan extraction electrode provided so as to be opposed to the emitter tipand constructed so as to surround the emitter tip, and a gas supply pipefor supplying gas to vicinity of the emitter tip, the ionization chamberhas the extraction electrode, a side wall provided juncturally toperiphery of the extraction electrode, and a top plate providedjuncturally to another end of the side wall, the extraction electrodehas a hole through which an ion beam from the emitter tip passes, andthe ionization chamber is almost closed except for the hole in theextraction electrode and the gas supply pipe, has therein anon-evaporable Getter material, and has a heating mechanism on theoutside.
 20. The ion beam device according to claim 19, wherein a gassupply path connected to the gas supply pipe is provided with a vesselcontaining a non-evaporable Getter material, and the vessel is connectedto an evacuation pump.